TW591869B - Flyback converter with synchronous rectifier - Google Patents

Abstract

The present invention aims to provide a flyback converter with a synchronous rectifier. A sensing impedance is employed to sense a secondary current and convert the secondary current into a control voltage before transmitting the control voltage to a controller. Then, by comparing the control voltage with a reference voltage, a control signal is clipped to drive a synchronous rectifier switch. At the same time, the present invention also provides a protection circuit of the flyback converter.

Description

591869 V. Description of the invention (1) [Technical field to which the invention belongs] The present invention relates to a flyback converter, and more particularly to a flyback converter having a synchronous rectifier. [Previous Technology] In recent years, 'switching power supply' (switching power supply) is developing rapidly, and it plays a very important role in computers and electronic products. Compared with the traditional power supply, the switching power supply has the advantages of stability, simplicity, and efficiency.

Among them, the flyback switching power supply is widely used because of its lower cost and simplified circuit design. In addition, synchronous rectification technology is also applied to the flyback converter. Figure 1 shows the prior art U.S. Pat. No. 6, 353, 544, which is a

Chi conversion device. It includes a flyback switching circuit 2000, a synchronous rectifier 300 ', a current transformer 400, and a load 500. This patent uses the above-mentioned current transformer 400 to sense the secondary-side current, and when the secondary-side current ends, it provides a high-frequency pulse to turn off the gate drive of the synchronous rectifier. Its main technical feature is the use of current transformers to achieve its purpose ’, but its disadvantage is its high price. Therefore, in order to reduce the cost, the present invention proposes a more effective solution. SUMMARY OF THE INVENTION The object of the present invention is to provide a flyback type with a synchronous rectifier.

591869 V. Description of the invention (2) The conversion device, the induced voltage and the synchronous voltage rectification are turned on to achieve the flyback conversion. The flyback is output to a high voltage transformer winding. Among them to the above-mentioned first pulse wave current. One induction is to use the inductive impedance to remove the salt due to the low cost of the induction. _ ^ ^ Β 电流 senses the primary current and sends its control power M to a control device ^ ^ Cuts out a control signal to promote a Related to this, the 4th plant protection circuit of the conversion device also mentions the above purpose at the same time. "The present invention wants φ ^ θ. Demonstrates a device with a synchronous rectifier and its protection circuit, including ... 3 switching circuits" coupling -Power V—. Its role is in frequency pulse voltage. The device includes at least a first winding, a second winding, and a third flyback switch circuit that outputs a high-frequency pulse wave and applies a% group, so that the second winding and the third winding generate high-frequency impedance and are coupled. The current output of the second winding. Its effect The t-frequency current is converted into a control voltage using Ohm's law. The impedance can be composed of general resistance, so the present invention achieves a fall-back method of 0 to control the output. A synchronous rectifier switch is coupled to the above-mentioned inductive impedance and pulse wave switch. A storage capacitor has a first terminal coupled to the synchronous rectifier switch. A control device is coupled to the control voltage. Wherein, when the control voltage is greater than or equal to a reference voltage, the control device will input a control signal to turn on the synchronous rectifier switch, so that the high-frequency pulse current can charge the storage capacitor; however, when the control

0535-9529TW (Nl); C92001; ROBERTLIU.ptd

591869 Description of the invention (3) The voltage is lower than the above reference step rectifier switch is turned off. When it ’s on, the above control signal is output to the same protection circuit, the first and second diodes of the same diode, and the second diode. The first positive electrode of the second diode is coupled with the first resistor of the third winding, the wheel 屮 ㈣ terminal of the control circuit of the first diode is coupled, and the positive electrode of the second diode is coupled with the potential. This protection is coupled, and the first resistor and a second ground malfunction. Prevents transient voltage rises

[Embodiment] Embodiment: Fig. 2 is a structural diagram showing the device of the present invention. During the development, the flyback converter power supply V of the β-step amplifier & amplifier includes a flyback switch circuit 1 connected to a device TR, including at least one limulus guanidine voltage. A transformer includes the first winding 2 and the second winding 3 in a bucket and a day a. Fuzhong, Bu, X, Chi switch circuit 1 output one ancient /, the above '

^ Pulses of the same frequency are applied to Shang Cheng 筮, so that the first-第 fine qL above the first winding 2 of the first winding 2 Leyi, 70, and 3 generates high-frequency pulse currents. The main feature of the present invention is the inductive impedance 4, output. "The purpose is to connect the above-mentioned high-frequency electrical connection to 4? -Ohm winding, and convert it into a control voltage v. Π ohm 疋 > sense a synchronous rectifier switch 5, coupled to the above-mentioned induced impedance 4 ^-stored electricity

591869 V. Description of the invention (4) ° Its first end is lightly connected to the synchronous rectifier switch 5 mentioned above. And, a control device is coupled to the control voltage ν_ and controls the movement of the synchronous rectifier switch 5 according to the control voltage Vsense of the inductive impedance 4. Wherein, when the control voltage is greater than or equal to a reference voltage, the control device outputs a control signal to synchronize the synchronization by 1 '^, so that the high-frequency pulse current can be applied to the stored electricity = line power. However, when the above-mentioned control voltage V is smaller than the closing of the door, the control signal is input to couple the synchronous rectifier switch 5 Γι η to the second terminal of the storage capacitor 7-the first-ground power to a second-to-ground The electrical impedance is connected to the first terminal of the synchronous rectifier switch 5 described above, which includes two resistors 9 and a third resistor 10, and the voltage dividing circuit 102 is composed of − The voltage divider circuit 702 can be generated = lost m is set to 8 and compared by a comparator η structure gas nse, it can cut V-4Tr; f, 切 and the control step rectifier switch 5 above. The workman then went to promote the above. Please refer to Figure 4. This figure shows a possible circuit diagram of the flyback converter of the present invention. : Kind: Step rectification-Inductive impedance 12, and the aforementioned synchronous rectification Inductive impedance 4 is used to receive the inductive impedance 12 ' open-source / drain coupling capacitor 7 input from the control device 6. Because of the control signal, the second on-resistance is the lowest, and it has a very high on-resistance with the effect of ^ == ^^^ This on-resistance value will not be on page 8 0535-9529TW (Nl); C92001; ROBERTLIU.ptd 591869 V. Description of invention (5): Decline. Therefore, the present invention can be used by the metal-oxide half field effect transistor, thereby reducing power consumption.偬 The figure shows the above control signal ν. The waveform diagram of ^ where yi is the voltage waveform of the first J winding 2 and V2 is the voltage across the above-mentioned second winding 3 = V'sense is the control voltage across the above-mentioned inductive impedance 4 and the wave signal is% It is the output waveform of the control device 6 described above. When electricity two and seven make ΓΓ high and V2 low, so ι is low and 彳 ir I · Γ is also low. When the time is just after 1: 1, V1 is low potential and V 2 is south potential. Tian | _μ v is also on V. _ Vsense is still potential, so the control signal = falling Λ position. With the increase of time, the voltage value of Vs_ is slowly ΐ I: the voltage value of Vsense is still more important than the voltage value of v-: the control signal vout is still high. When t time increases to t2, Β: before the human-side current ends (time is t3), at this time the voltage of vsense is turned on, and the voltage value 'makes the control signal v-transition to s: e potential close field The voltage of the effect transistor 13 before the end of the secondary-side current is advanced: after 22 to 12, the voltage value of Vsense is less than the electric value of Vref at this time, so that the control signal U continues at a low potential. f shows the flyback conversion i14 circuit diagram of the present invention with a synchronous rectifier, wherein the above-mentioned transformer τι ^ has-the third winding 20 includes a 1_ ^ group 14 lightly connected protection circuit 2 (3. The above protection circuit 22 Distinguish MC; the first one-pole body (15, 16), in which the above-mentioned first connection, the cathode of the i-th, 16) is coupled to the first end of a first resistor 17, and the anode of the = is connected to the first The anode of the pole body 16 on the second end of the three windings 14 is coupled to the output end of the control circuit 11

591869 Brief Description of Drawings Figure 1 shows a conventional flyback converter with synchronous rectification. Fig. 2 shows a synchronous rectification flyback converter according to the present invention. Figure 3 is a detailed block diagram showing the control device. Fig. 4 is a complete circuit diagram showing a synchronous rectification flyback converter of the present invention. Fig. 5 is a diagram showing a voltage waveform of the present invention. # FIG. 6 is a diagram showing a flyback converter with a synchronous rectifier and a protection circuit according to the present invention. [Symbol description] 1 ~ Flyback switch circuit 2 ~ First winding 3 ~ Second winding 4 ~ Inductive impedance 5 ~ Synchronous rectifier switch 6 ~ Control device 7 ~ Storage capacitor 8 ~ Comparative device 9 ~ Second resistor 1 0 ~ Third resistance

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Claims (1)

591869 6. Scope of patent application ^ A synchronous rectifier flyback converter device, including. Electric & flyback switch circuit 'lightly connected to a power source to turn out a high-frequency pulse wave The above-mentioned force to 2 including a first winding And the second winding is generated-up to the first-winding 'so that the first is used to convert the current wheel * ML of the second winding to a control voltage; a synchronous rectifier switch is coupled to the inductive impedance; And: the first terminal of the storage order state is coupled to the synchronous rectifier switch; a control device is coupled to the control voltage; when the output is a binary I control voltage greater than or equal to the -reference voltage, the pulse current is correct. The storage capacitor is charged; when the frequency is lower than the reference voltage, the control signal is output; and the current switch is turned off.观 ^ The above steps are integrated into the following steps: The flyback conversion device with a synchronous rectifier as described in the first item of the scope of the above-mentioned +, the control device includes: an inverse voltage divider circuit for generating the above Reference voltage; and voltage. A comparison device is used to compare the above control voltage and the above reference voltage. The flyback converter with synchronous rectifier described in item 2 of the patent scope is used, wherein the voltage dividing circuit is composed of a resistor. 0535-9529TWFl (Nl); C92001; ROBERTLIU.ptc Page 13 59 Chi-style 4-turn designation with the synchronous rectifier as described in item 2 of the second paragraph 92101095 VI. Patent application scope Chi Qi ^ Please refer to the patent scope of the first item with a synchronous rectifier-type 4-way conversion with synchronous rectifier, The above-mentioned inductive impedance is a jumper type composed of a resistor. Please refer to the counter-current body 1 with a synchronous rectifier described in the first item of the patent scope. The synchronous rectification opening relationship is -metal-oxygen half field effect. Connected to the above-mentioned inductive impedance, the gate is 1 ', and the second source / output is the output terminal of the flyback conversion device with a synchronous integer. The anti-earth i-position with synchronous rectifier as described in item 6 of the 7-m range of the Chi type: the second end of the above storage capacitor is coupled-the first-source " and the second drain is connected to a second ground potential up to golden milk "Effective transistor No.-8.-A flyback conversion device with a synchronous rectifier, including a voltage flyback switch circuit 'lightly connected to a power source to output a high-frequency pulse: two: Shi Shao included- A winding, a second winding, and a third winding: "I produces 脉 I pulse is applied to the above-mentioned winding, so that the first% group generates a 咼 frequency pulse current; 疋 the above; change; the winding current output ， Synchronous rectifier switch, face ΓΓ; inductive impedance; a storage capacitor, the first of which is a μ, +, and gate-control device, lightly connected to the synchronous rectifier 591869 Case No. 921010QR 6. The scope of patent application Among them, when the above control outputs a control signal to obtain the above-mentioned pulse current to the above-mentioned stored reference voltage, the current switch is turned off; and a protection circuit including a first diode and a second diode The connection between the anode of the cathode diode and the first anode, the second end of the control circuit, and the synchronous rectifier switch of the third winding. With a comparison device, it is dropped on the voltage. When the voltage is greater than or equal to a reference voltage, the synchronous rectification switch is turned on, so that the high-frequency capacitor is charged; when the control voltage is output, the control signal is output to synchronize the first and second diodes, wherein the first and The first end of the first resistor is coupled, the second end of the first and second windings are connected, the output end of the second diode is connected, and the end of the brother of the first resistance is connected to the inductive impedance and the upper point. . /. The inverse control circuit with a synchronous rectifier according to item 8 includes: generating a reference voltage; and comparing the first control voltage with the reference 驮 + ^ as described in item 9 of the patent scope 5 other type conversion device 'Where the above voltage dividing circuit is composed of resistance ^. As described in the patent application No. 8 of the 5-ch conversion device with synchronous rectifier, straight φ μ 4 less / host The comparison device of the above and below is composed of a comparator. The Chi-type conversion, such as the installation of /, specifically Λ Fan Shang Wai, ,,, and the above impedance components are composed of resistors. The flyback type is changed as described in the Λ patent Λ Wai twelfth item of the Λ with a synchronous rectifier in the second terminal of the storage capacitor is coupled to 591869 Amendment No. 92101095 6. Scope of patent application A ground potential, and the second end of the third winding, the inductive impedance and the connection point of the synchronous rectifier switch are coupled to a second ground potential. 1 4. The flyback conversion device with a synchronous rectifier as described in item 13 of the scope of the patent application, wherein the synchronous rectification on-off relationship is a metal-oxygen half field-effect transistor. 0535 > 9529TWFl (Nl); C92001; ROBERTLIU.ptc Page 16