TW200529541A - Asymmetric half-bridge forward converter - Google Patents

Abstract

An asymmetric half-bridge forward converter circuit is suitably applied in a low-profile system. The invented circuit is able to not only reduce the switching noises and switching loss for a semiconductor switch during operation, but also increase the overall efficiency of the converter by the synchronous rectification control technique, thereby improving the circuit design in the conventional skill. Furthermore, the use of an externally applied harmonic inductance is easier to achieve a zero voltage switching for a switch, and the externally applied saturated inductance can effective reduce electromagnetic interference (EMI).

Description

200529541 V. Description of the invention (1) [Technical field to which the invention belongs] The present invention relates to the creation of an asymmetric half-bridge forward converter circuit architecture with a dual-transformer synchronous rectification control function, and aims to provide a high efficiency and Forward converter circuit for thinner purpose. [Prior art]

According to the so-called forward converter (F 1〇rward C ο η verter), it is a power conversion architecture that converts DC voltage to different DC voltages, and its function is similar to a flyback converter (F 1 yback C0nverter) However, when a forward power converter is used, because the energy only passes through the transformer, it is suitable for the use of smaller transformers, and is widely used in power supplies with low output voltage and large output current. In addition, for the power supply of general computer systems, the stability and adequacy of the power supply are necessary; however, the biggest problem of power transmission with low output voltage and large output current is the power loss and heat consumption in the output stage. Traditional linear output The stage provides continuous voltage to the computer system; however, this method will waste a lot of power. Therefore, the transmission is adjusted by the pulse width (P u 1 s e W i

dth M〇du 1 ati〇n) The technology of chopping the output voltage of the transformer into pulses, by changing the width, number or distribution rules of the pulses, in order to change the value and frequency of the output voltage to maximize the energy transmission technology, plus the aforementioned 'The forward converter (F 1 ◦ r C ο η verter) is suitable for the characteristics of smaller transformers, and should be more suitable for applications in thin systems (L 〇w — P r 〇fi 1 e). However, due to the power loss in the same power supply system,

Page 6 200529541 V. Description of the invention (2). It may occur in the power consumption of the transformer, and the high temperature generated by the transformer is converted by the power consumed, so in the thin (1 ^ 〇 \ ¥ — P How to reduce the power consumption of the transformer in the system of 〇fi 1 e) will be regarded as another important issue. [Summary of the Invention] The "asymmetric half-bridge forward converter" of the present invention is a high-efficiency power conversion circuit, which controls the operation of the circuit by the switching of semiconductor switches (hereinafter collectively referred to as switching elements), and uses resonant inductance The charge and discharge of the switch's parasitic capacitance can achieve zero voltage conduction of the switch, which can reduce the switching loss. Therefore, when using two transformers, the magnetic component can be thinned, and the power consumed by it can be appropriately distributed on the two transformers, which will not cause the problem of transformer overheating. [Implementation method] In order to make your reviewing committee aware of the structure and overall operation of the present invention, the following diagrams are used to explain it: The "asymmetric half-bridge forward converter" of the present invention is a high The efficiency power conversion circuit controls the operation of the circuit by switching the switching element, and uses the current of the resonant inductor to charge and discharge the parasitic capacitance of the switching element to achieve zero-voltage conduction of the switching element, which can reduce the switching loss. First, as shown in the first figure, it is a circuit configuration diagram of the first embodiment of the asymmetric half-bridge forward converter circuit of the present invention. The entire circuit architecture is connected to the first and second transformers T 1, T 2 input primary side and

200529541 V. Description of the invention (3) A main switching element Q 1 and a sub switching element Q 2 are arranged between the lines constituting the control circuit 10, and a first parasitic element 2 is arranged between two contacts of the main switching element Q 1 A second parasitic diode D 2 and a second parasitic capacitor C 2 are arranged between the two contacts of the secondary switching element Q 2 of the polar body D 1 and the first parasitic capacitor C 1, and are respectively disposed on the main switching element. The first saturation inductor L 1 and the second saturation inductor L 2 are provided at the path of one of the contacts of Q 1 and the auxiliary switching element Q 2, and the control circuit 10 of the first transformer T 1 and the second transformer T 2 is provided by PW Μ control circuit IC 1 and drive control circuit IC 2 are implemented; in addition, a resonant inductor L 3 and a blocking capacitor C are added to the primary side of the first and second transformers T 1, D 2 and control circuit 10 0. 3.俾 The resonance resonant inductor L 3 is used to achieve the resonance function, so that the leakage inductance of the first and second transformers TI and T2 and the first parasitic capacitance C 1 and the second parasitic capacitance C 2 are blind between the switches ( dead time) to generate resonance to achieve zero-voltage switching of the main switching element Q 1 and the sub switching element Q 2 respectively; of course, its resonance inductance L 3 can also be arranged on the first and second transformers as shown in the fifth figure The secondary side of T 1 and T 2 can also achieve the same effect. In addition, since the blocking capacitor C 3 (b 1 0 c k i n g capacitor) is large enough, the voltage across it can be regarded as a constant value. As for the output secondary sides of the first and second transformers T 1 and T 2, the secondary windings of the first and second transformers T 1 and T 2 plus the first rectifying diode D 3 and the second rectifying Diode D 4, or the first synchronous rectifier switch Q 3 and the second synchronous rectifier switch Q 4 are used, and the first filter

200529541 V. Description of the invention (4) A rectifier filter circuit 20 composed of a capacitor C 4, a second filter capacitor C 5 and a filter inductor L 4 is achieved. In this circuit architecture, the duty cycle (duty eye 1 e) of the main switching element Q 1 and the sub switching element Q 2 is different and complementary, so it is called an asymmetrical architecture. Because the first and second transformers T 1 and T 2 can be used to reduce the thickness of this magnetic component, and the power consumed by it can be appropriately distributed on the two transformers, it will not cause the problem of transformer overheating; especially, the first A transformer T 1 and a second transformer T 2 respectively play the role of a normal operating transformer and an energy storage inductor at different periods. When the main switching element Q 1 is turned on, the first transformer T 1 is regarded as a normally operating transformer to transmit energy. To the secondary side, at the same time, the second transformer T 2 is charged as an energy storage inductor; conversely, when the auxiliary switching element Q 2 is turned on, the second transformer T 2 is regarded as a normally operating transformer to transmit energy to the secondary Side, and the first transformer T 1 is regarded as an energy storage inductor to store energy. Furthermore, the working principle of the circuit architecture shown in the first diagram (the first embodiment) and the zero-voltage conduction mechanism are further described as follows: As shown in the second diagram, when the main switching element Q 1 is turned on and the auxiliary switching element Q At the time of cut-off, the current flows from the input power terminal V i η into the blocking capacitor C 3, the primary winding of the first transformer T 1 and the second transformer T 2, the external resonant inductor L 3, and the main switching element Q 1 and the first A saturated inductance L 1, at which time energy is transmitted to the secondary winding through the first transformer T 1, and is transmitted through the first synchronous rectification switch Q 3 or the first rectification diode D 3, and the rectification filter circuit 20. To the output load, at this time the second transformer

200529541 V. Description of the invention (5) The device T 2 acts like an inductor and stores energy in the winding. Then, if the main switch Q 1 is turned off, the current that originally flows through the main switching element Q 1 will first parasitize the main switching element Q 1 and the sub switching element Q 2 respectively. The capacitor C1 and the second parasitic capacitor C 2 charge and discharge (charge the first parasitic capacitance C 1 and discharge the second parasitic capacitance C 2), at this time, the voltage across the drain-source terminal of the main switching element Q 1 starts to rise in the form of resonance When the cross-voltage across the drain-source terminal of the main switching element Q 1 rises to the input voltage, the second parasitic diode D 2 of the auxiliary switching element Q 2 will be conducted in a forward direction, so that the auxiliary switching element Q 2 The voltage across the drain-source is clamped at zero voltage. If the resonance current of the primary side is in the reverse direction, that is, before the second parasitic diode D 2 of the auxiliary switching element Q 2 is turned off, the control signal of the driving control circuit IC 2 can turn on the auxiliary switching element Q 2, that is, Zero voltage conduction of the secondary switching element Q 2 can be achieved. Therefore, when the secondary switching element Q 2 is turned on and the main switching element Q 1 is turned off, as shown in the third figure, the energy stored in the blocking capacitor C 3 is transmitted to the secondary winding through the second transformer T 2 and passes through The second synchronous rectifier switch Q 4 or the second rectifier diode D 4 and the rectifier filter circuit 20 are transmitted to the output load end. At this time, the first transformer T 1 acts as an inductor and stores energy in the winding. Similarly, immediately when the sub-switching element Q 2 is turned off, the current that originally flows through the sub-switching element Q 2 will cause the first parasitic capacitances C 1 and The two parasitic capacitors C 2 are charged and discharged (the first parasitic capacitor C 1 is discharged, and the second parasitic capacitor C 2 is charged). At this time, the drain between the main switching element Q 1 and the source terminal

Page 10 200529541 V. Description of the invention (6) The voltage starts to decrease in the form of resonance. When the voltage across the main switching element Q 1 drain-source drops to zero voltage, it will make the first switching element Q 1 The parasitic diode D 1 is conducted in a forward direction, so that the voltage across the drain of the main switching element Q 1 to the source is clamped to zero voltage. If the resonance current of this primary side is before the reverse direction, that is, before the first parasitic diode D 1 of the main switching element Q 1 is turned off, the control signal of the drive control circuit IC 2 can turn on the main switching element Q 1, that is, Zero-voltage conduction of the main switching element Q 1 can be achieved. As for the voltage conversion relationship between the output voltage and the input voltage, it can be expressed as follows: V ο / V i η Two [D (lD)] / [(Np 1 / N s 1) D + (N P2 / Ns2) (lD) ]; Here D represents the duty cycle (Duty Cycle) of the main switch, N p 1 / N s 1 is the ratio of the primary side to the secondary side of the first transformer T 1, and N p 2 / N s 2 is the first The ratio of the number of turns on the primary and secondary sides of the two transformers T 2. Of course, the circuit architecture of the present invention can also move the main switching element Q 1 from the lower bridge to the upper bridge, and move the auxiliary switching element Q 2 from the upper bridge to the lower bridge, as shown in the fourth figure, and its related operating principle The circuit structure is the same as the previous embodiment, and it also has the function of multiple transformer synchronous rectification. As mentioned above, the present invention provides an asymmetric half-bridge forward converter circuit architecture that can achieve high efficiency and thinness, and filed an application for an invention patent according to the law; however, the above implementation description and drawings show that It is one of the preferred embodiments of the present invention, and is not intended to limit the present invention.

200529541

Page 12 200529541 Brief description of the drawings The first diagram is a schematic diagram of the circuit configuration architecture of the first embodiment of the present invention. The second diagram is the schematic diagram of the circuit operation state when the main switching element Q 1 is turned on in the first embodiment of the present invention. The third diagram is a schematic diagram of the circuit operation state when the auxiliary switching element Q 2 is turned on in the first embodiment of the present invention. The fourth diagram is a schematic diagram of the circuit configuration architecture of the second embodiment of the present invention. The fifth diagram is the first diagram of the present invention. Schematic diagram of the circuit configuration and architecture of the second embodiment. [Description of Symbols of Components] C 1 First parasitic capacitor C 2 Second parasitic capacitor C 3 Blocking capacitor C 4 First> Wave capacitor C 5 Second wave capacitor D 1 First parasitic Diode D 2 Second parasitic diode Body D 3 First rectifier diode D 4 Second rectifier body IC 1 PW Μ Control circuit IC 2 Drive control circuit L 1 • Saturation inductance L 2 • Saturation inductance L 3 • Resonance inductance L 4 Filter inductance

Page 13 200529541 Schematic description

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Claims (1)

200529541_ 6. Application patent scope 1. One kind of "asymmetric half-bridge forward converter" is provided with a main switching element and a sub-switching element between two lines connected in series with the input side of the transformer and the control circuit. Among the transformers, a first parasitic diode and a first parasitic capacitor are arranged between two contacts of the main switching element, and a second parasitic diode is arranged between two contacts of the auxiliary switching element. And the second parasitic capacitor; in addition, a resonant inductor and a blocking capacitor are added to the primary side of the two transformers connected to the control circuit; the resonant resonant inductor is used to achieve the resonance function, so that the leakage inductance of the two transformers and the first parasitic capacitor Resonance with the second parasitic capacitance occurs when the switches are blind, so as to reach the zero-voltage switchers of the main switching element and the sub-switching element, respectively. 2. An "asymmetric half-bridge forward converter" is provided with a main switching element and a sub-switching element between the lines connecting the input primary side of two transformers in series with the control circuit. Among the transformers, the main switch A first parasitic diode and a first parasitic capacitor are arranged between two contacts of the element, and a second parasitic diode and a second parasitic capacitor are arranged between the two contacts of the auxiliary switching element; A blocking capacitor is added to the primary side of the two transformers and the control circuit, and a resonant inductor is added to the secondary side of the two transformers. The resonant resonant inductor is used to achieve the resonance function, so that the leakage inductance and A parasitic capacitor and a second parasitic capacitor generate resonance when the switches are blind, so as to reach the zero-voltage switchers of the main switching element and the sub-switching element, respectively. 3. The "asymmetric half-bridge forward converter" as described in item 1 or 2 of the scope of patent application, wherein the output secondary side of the two series transformers is the secondary winding of the two transformers plus the first Rectifier diode and second rectifier Page 15 200529541 VI. Scope of Patent Application Diodes and those who achieve rectifier and filter circuits. 4. The "asymmetric half-bridge forward converter" as described in item 1 or 2 of the scope of patent application, wherein the output secondary side of the two series transformers is the secondary winding of the two transformers plus the first A synchronous rectifier switch, a second rectifier switch, and a rectifier filter circuit. 5. The "asymmetric half-bridge forward converter" as described in item 2 of the scope of the patent application, wherein the output secondary side of the two series transformers is the secondary winding of the two transformers plus the first rectifying diode. It is achieved with a second rectifier diode and a rectifier filter circuit. The rectifier filter circuit is composed of a first filter capacitor, a second filter capacitor and a filter inductor. 6. The "asymmetric half-bridge forward converter" as described in item 1 or 2 of the scope of patent application, wherein the output secondary side of the two series transformers is the secondary winding of the two transformers plus the first This is achieved by a synchronous rectifier switch, a second rectifier switch, and a rectifier filter circuit. The rectifier filter circuit is composed of a first filter capacitor, a second filter capacitor, and a filter inductor. 7. The "asymmetric half-bridge forward converter" as described in item 1 or 2 of the scope of patent application, wherein the control circuit is implemented by a PWM control circuit and a drive control circuit. 8. The "asymmetric half-bridge forward converter" as described in item 1 or 2 of the scope of patent application, wherein a first saturation inductance is provided at a path of one of the contacts of the main switching element, and the auxiliary switch A second saturation inductor is provided at a path of one of the contacts of the component. Page 16