WO2013075401A1 - 一种电源电路 - Google Patents

一种电源电路 Download PDF

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Publication number
WO2013075401A1
WO2013075401A1 PCT/CN2012/070137 CN2012070137W WO2013075401A1 WO 2013075401 A1 WO2013075401 A1 WO 2013075401A1 CN 2012070137 W CN2012070137 W CN 2012070137W WO 2013075401 A1 WO2013075401 A1 WO 2013075401A1
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Prior art keywords
capacitor
boost
diode
circuit
power supply
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PCT/CN2012/070137
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English (en)
French (fr)
Inventor
黄天华
余凤兵
胡建仁
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广州金升阳科技有限公司
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Publication of WO2013075401A1 publication Critical patent/WO2013075401A1/zh

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac

Definitions

  • the present invention relates to a power supply circuit, and more particularly to a capacitively isolated DC/DC converter. Background technique
  • the electromagnetic transformer achieves the purpose of energy transmission by winding two or more windings on the same core, and realizing the change of the primary and secondary voltages, currents, and impedances according to the electromagnetic induction principle.
  • the electromagnetic transformer has been widely used because of its advantages of high transmission power density and good load regulation.
  • the structure of the electromagnetic transformer determines the low level of automation of its processing, and its production and processing is still labor intensive. Therefore, for some micro power supply modules with extremely simple structure, the transformer process and its assembly process in the product manufacturing process take too much time, which increases the total cost of the product. Especially in the era of rising labor costs, reducing labor costs has become an urgent problem to be solved.
  • a capacitor can be used as an electrical isolation device and has the function of energy transmission.
  • the inductor and the capacitor are connected in series to generate resonance to realize input and output isolation and energy energy transmission.
  • the Chinese Patent Application Publication No. 201010287926.5, the publication number is CA2141389A1.
  • the Canadian Patent Specification and the Canadian Patent Specification Publication No. CA2131689A1 disclose a power supply device using capacitive isolation, which employs an energy transfer method by controlling the switching frequency through a half bridge or a full bridge circuit.
  • the input end of the network generates a frequency-adjustable square wave signal (mainly for frequency stabilization to achieve a stable output voltage) to change the impedance of the resonant network, thereby achieving adjustment of the output voltage.
  • the three power supply units are all in the form of a full-bridge or half-bridge topology.
  • the half-bridge circuit requires two switching tubes, and the full-bridge circuit requires four switching tubes.
  • the two switching tubes of the bridge arm need to be driven by isolation, and the dead time of the two switching tube driving signals of the same bridge arm is artificially added to prevent the straight-through phenomenon.
  • FIG. 1 shows a conventional Boost boost circuit including a driving circuit, a boosting inductor L1, a switching transistor Q1, a boosting diode D1, and an output filter capacitor C1; and a voltage input terminal Vin connected to the switching transistor Q1 through a boosting inductor L1.
  • the output of the driving circuit is connected to the gate of the switching transistor Q1, the source of the switching transistor Q1 is connected to the voltage reference terminal, the drain thereof is connected to the anode of the boosting diode D1, and the cathode of the boosting diode D1 is filtered by the output.
  • Capacitor C1 is connected to the source of switch Q1, and both ends of output filter capacitor C1 are the output of the circuit, and load R is connected therebetween.
  • the output filter capacitor can be an electrolytic capacitor or a non-polar capacitor. If an electrolytic capacitor is used, the cathode of the boost diode D1 should be connected to the anode of the electrolytic capacitor.
  • the working process of the circuit is as follows: During the turn-on of the switch Q1, the boost inductor L1 is stored under the excitation of the input power supply, and the load energy is provided by the output filter capacitor. During the turn-off of the switch Q1, the boost inductor L1 passes through the boost diode D1. The output filter capacitor C1 is charged while supplying energy to the load.
  • the operating waveform of the circuit is shown in Figure 2. It can be known from the working process of the circuit that the conventional Boost circuit topology can only be used for boost conversion, that is, the output voltage must be greater than the input voltage.
  • the switching tube in the conventional Boost boost circuit can be implemented by a MOSFET or a triode. The above description is based on the MOSFET, and the implementation principle of the triode is the same, and will not be described again. Summary of the invention
  • a power supply circuit includes a Boost boost circuit, and further includes a second capacitor, a third capacitor, and a second diode; and a second capacitor is connected to a connection point of the switch tube and the boost inductor in the Boost boost circuit
  • the cathode of the boost diode is sequentially connected to the voltage reference terminal through the output filter capacitor and the third capacitor in the Boost boost circuit, the cathode of the second diode and the riser The anode of the voltage diode is connected, and the anode of the second diode is connected to the third capacitor and the output filter capacitor Contact.
  • the fourth capacitor is further included; the fourth capacitor is connected between the connection point of the switching tube and the boosting inductor and the voltage reference end.
  • the fifth capacitor is further included; the fifth capacitor is connected in parallel with the boost inductor.
  • the fourth capacitor and the fifth capacitor are further included; the fourth capacitor is connected between the connection point of the switch tube and the boost inductor and the voltage reference terminal; and the fifth capacitor is connected in parallel with the boost inductor.
  • a voltage stabilizing circuit is further included; a voltage stabilizing circuit is connected between the output filter capacitor and the load.
  • a feedback control circuit is also included; a feedback control circuit is connected between the output of the Boost boost circuit and the drive circuit.
  • the object of the invention can also be achieved by the following technical measures:
  • a power supply circuit includes a Boost boost circuit, further comprising a second capacitor, a third capacitor, a fourth diode, a fifth diode, and a sixth diode; and a second capacitor connected to the Boost boost circuit
  • the cathode of the boost diode sequentially passes through the output filter capacitor, the sixth diode and the third in the Boost boost circuit
  • the capacitor is connected to the voltage reference terminal, wherein the cathode of the sixth diode is connected to the third capacitor, the cathode of the fourth diode is connected to the cathode of the boost diode, and the anode is connected to the sixth diode
  • the cathode, the cathode of the fifth diode is connected to the anode of the boost diode, and the anode is connected to the anode of the sixth diode.
  • the fourth capacitor is further included; the fourth capacitor is connected between the connection point of the switching tube and the boosting inductor and the voltage reference end.
  • the fifth capacitor is further included; the fifth capacitor is connected in parallel with the boost inductor.
  • the fourth capacitor and the fifth capacitor are further included; the fourth capacitor is connected between the connection point of the switch tube and the boost inductor and the voltage reference terminal; and the fifth capacitor is connected in parallel with the boost inductor.
  • the present invention has the following beneficial effects:
  • the invention uses capacitive coupling to transmit energy, instead of the traditional transformer transmission, realizes the electrical isolation of the original secondary side of the circuit.
  • the invention only needs to adopt a single switching tube and a single inductor, and the energy can be realized by the isolation capacitor of the primary and secondary sides.
  • the transmission overcomes the problems of complicated process and high labor cost when the switching power supply is isolated by the electromagnetic transformer, and the complicated circuit of the half bridge or the full bridge circuit in the conventional capacitive isolation scheme, the cost is high, and it is not easy to be miniaturized, so
  • the invention simplifies the production process of the product, greatly It saves labor costs, has the characteristics of easy realization of low cost and miniaturization, and is especially suitable for micro power and low power switching power supply occasions.
  • Figure 1 is a circuit schematic diagram of a conventional Boost boost circuit
  • Figure 2 is a waveform diagram of the Boost boost circuit when it is operating
  • Embodiment 3 is a diagram of an evolution circuit diagram of Embodiment 1 of the present invention.
  • FIG. 4 is a second diagram of an evolution circuit diagram according to Embodiment 1 of the present invention.
  • FIG. 5 is a working waveform diagram of the circuit shown in Figure 4.
  • FIG. 6 is a schematic circuit diagram of a first embodiment of the present invention.
  • FIG. 7 is a schematic circuit diagram of a second embodiment of the present invention.
  • Embodiment 8 is a working waveform diagram of Embodiment 2 of the present invention.
  • FIG. 9 is a schematic circuit diagram of a third embodiment of the present invention.
  • FIG. 10 is a schematic circuit diagram of a fourth embodiment of the present invention.
  • FIG. 11 is a schematic circuit diagram of a fifth embodiment of the present invention.
  • FIG. 12 is a schematic circuit diagram of a sixth embodiment of the present invention.
  • FIG. 6 shows a power supply circuit according to the first embodiment of the present invention, including a Boost boost circuit, a capacitor C2, a diode D2, and a capacitor C3; the Boost boost circuit is connected in the same manner as the circuit shown in FIG. 1, and the drain of the switch Q1 is shown.
  • the cathode of the diode D1 is sequentially connected to the voltage reference terminal through the output filter capacitor C1 and the capacitor C3, and the connection point of the output filter capacitor C1 and the capacitor C3 is connected to the anode of the diode D2, the diode
  • the cathode of D2 is connected to the anode of boost diode D1.
  • the capacitor C2, the diode D2 and the capacitor C3 in the first embodiment of the present invention are gradually added based on the conventional Boost boost circuit (as shown in FIG. 1).
  • the circuit based on FIGS. 3 and 5 illustrates the conventional Boost boost circuit according to the present invention. How to gradually evolve into a capacitive isolated single tube DC/straight according to the first embodiment of the present invention
  • the flow converter achieves the purpose of transmitting energy while the original secondary side is isolated while using only a single switching tube and a single inductor with an isolated capacitor.
  • the present invention is substantially different from the Boost boost circuit.
  • the Boost circuit can only be used for boosting, and the present invention can not only boost but also step down, which is a brand new topology structure, The technical personnel in the field understand the working principle of the circuit, and then the Boost boost circuit is gradually evolved here.
  • a capacitor C2 is connected in series between the anode of the diode D1 and the drain of the switching transistor Q1.
  • the charge on the capacitor C2 is not unidirectional due to the unidirectional conductivity of the diode D1, so the circuit shown in Fig. 1 does not operate normally.
  • a diode D2 is connected in series between the anode of the diode D1 and the source of the switching transistor Q1, and the cathode of the diode D2 is connected to the anode of the diode D1, and the diode D2 is connected.
  • the anode is connected to the source of the switching transistor Q1.
  • the capacitor C2 has a discharge loop.
  • the circuit shown in Figure 4 can work normally. Due to the voltage division of the capacitor C2, the circuit can not only realize the boost, but also has a reasonable parameter design, and can also realize the step-down, the circuit.
  • the working principle is as follows: During the conduction of the switch Q1, the boost inductor L1 is stored under the excitation of the input power, and the load energy is provided by the output filter capacitor C1. During the turn-off of the switch Q1, the boost inductor L1 charges the output filter capacitor C1 while supplying energy to the load R through the capacitor C2 and the diode D1. During this period, the voltage at point B is clamped at the output due to the conduction of the diode D1. Voltage, point A voltage Since the current in the same direction flows through the capacitor C2, the voltage reaches the peak when the boost inductor L1 current drops to zero. After the energy in the boost inductor L1 has been released, the diode D1 turns off.
  • the voltage at point B is clamped by diode D2, and the potential at point A is pulled down.
  • the inductor L1 and capacitor C2 pass through the diode D2, and the input power source forms a resonance. Since the input power can be regarded as As a large capacitor, the potential at point A changes slowly until the switch Q1 is turned on again, destroying the resonance condition.
  • the energy stored in the capacitor C2 is discharged through the discharge circuit formed by the switch Q1 and the diode D2, and the energy stored in the capacitor C2 is reset. Then, the next working cycle is started.
  • the working waveform of the circuit shown in Figure 4 is shown in Figure 5.
  • the power supply circuit of the first embodiment of the present invention shown in FIG. 6 is based on the circuit shown in FIG. 4, and a capacitor C3 is connected in series between the connection point of the anode of the diode D2 and the output filter capacitor C1 and the source of the switch transistor Q1.
  • Capacitor C2 and capacitor C3 form electrical isolation between the primary side (input side) and the secondary side (output side) of the power supply circuit.
  • the dotted line in the figure is the isolation point, and the left side of the dotted line corresponds to the primary side (input side). Right phase On the secondary side (output side).
  • the diode D1, the diode D2, the output filter capacitor C1 and the load of the circuit are equivalent to an equivalent load, then the capacitor C2, the capacitor C3 and the equivalent load form a series circuit, so the capacitor C2 and the capacitor can be C3 is equivalent to a capacitor, so the first embodiment of the present invention operates in the same manner as the circuit shown in FIG.
  • the entire voltage loop includes the boost inductor L1, the capacitor C2, the diode D1, the load R, the capacitor C3, and the circuit. Input power.
  • the voltage on the output load is the difference between the input supply voltage and the voltage of all other voltage divider devices on the series circuit. This process can also be regarded as a damped oscillation process.
  • Embodiment 2 Embodiment 2
  • FIG. 7 shows a power supply circuit according to a second embodiment of the present invention, which has substantially the same circuit configuration and working principle as the first embodiment of the present invention. The difference is that the capacitor C4 is added, and the capacitor C4 is connected to the source and the drain of the switch Q1.
  • Capacitor C4 can achieve the ideal buffering effect, improve the voltage waveform of the drain (point A) of the switch Q1 in the circuit (as shown in Figure 8), that is, reduce the drain of the switch Q1 when it is turned off (A Point)
  • the rising rate of voltage ⁇ / to achieve the soft opening effect of the circuit, thereby reducing the noise of the circuit, improving its EMC characteristics, reducing the loss of the switching tube through soft switching, is conducive to the improvement of frequency and power circuit products miniaturization.
  • the capacitor C4 forms a parallel structure with the branch formed by the capacitor C2, the capacitor C3 and the output equivalent load. Therefore, if the other parameters are constant, increasing the capacitor C4 will inevitably result in a decrease in output power.
  • the waveform of the drain voltage of the approximately sinusoidal switch transistor Q1 and the zero voltage of the switch transistor Q1 can improve the conversion efficiency of the circuit while greatly increasing the operating frequency.
  • FIG. 9 shows a power supply circuit according to a third embodiment of the present invention, which has substantially the same circuit configuration and operation principle as the second embodiment of the present invention, except that the capacitor C4 is connected in parallel with the boost inductor L1.
  • the working essence and final effect of the third embodiment and the second embodiment are completely identical.
  • the fundamental reason is that for high-frequency signals, the input power supply can be regarded as a short circuit because its potential is constant, so there is no difference between the capacitor C1 in parallel with the boosting inductor L1 and the drain-source connected to the switching transistor Q1.
  • the third embodiment has the same working waveform as the second embodiment (as shown in FIG. 8).
  • Embodiment 4 has the same working waveform as the second embodiment (as shown in FIG. 8).
  • FIG. 10 is a diagram showing a power supply circuit according to a fourth embodiment of the present invention, which has substantially the same circuit configuration and operation principle as the first embodiment of the present invention, except that on the output side of the circuit, a full bridge rectifier circuit is used instead of the first embodiment.
  • a half-bridge rectifier circuit composed of a diode D1 and a diode D2 the full-bridge rectifier circuit includes a diode D3, a diode D4, a diode D5, and a diode D6.
  • the anode of the diode D3 is connected to one end of the output side of the capacitor C2, and the cathode and capacitor of the diode D6 are connected.
  • the cathode of the diode D3 is connected to the cathode of the diode D4
  • the anode of the diode D4 is connected to the cathode of the diode D6
  • the anode of the diode D6 is connected to the anode of the diode D5
  • the cathode of the diode D5 is connected to the cathode of the diode D3.
  • the anode, capacitor C1 is connected between the cathode of diode D4 and the anode of diode D6.
  • Fig. 11 shows a power supply circuit according to a fifth embodiment of the present invention, which has substantially the same circuit configuration and operation principle as the first embodiment of the present invention, and the difference is that a voltage stabilizing circuit is added between the output filter capacitor C1 and the load R.
  • a voltage stabilizing circuit is added between the output filter capacitor C1 and the load R.
  • FIG. 12 is a diagram showing a power supply circuit according to a sixth embodiment of the present invention, which has substantially the same circuit configuration and working principle as the first embodiment of the present invention. The difference is that the feedback control circuit further includes voltage sampling, error amplification, and isolation coupling. PFM adjustment and other main links, which are connected to the output of the circuit and the drive circuit Between, the circuit becomes a closed loop structure of the output voltage.
  • the working principle of the sixth embodiment is as follows: From the analysis of the above embodiment, it is known that the output load voltage is related to the inductance of the circuit loop and the voltage division of the capacitor during resonance. At the same time, the impedance of the capacitor to the AC signal is ⁇ The impedance of the inductor to the AC signal is ⁇ £.
  • the voltage division on the inductor or capacitor is changed to achieve the purpose of adjusting the amplitude of the output voltage. It is also because of this mechanism that the present invention can achieve the boost and buck outputs.
  • the output voltage changes the voltage is sampled through the voltage divider network at the output, and the sample voltage is compared with the reference voltage to generate an error signal.
  • the signal is amplified by the optocoupler and transmitted to the primary side, and participates in the control of the PFM regulation circuit. Thereby playing the role of adjusting the driving frequency. Achieve stability of the output voltage.
  • the advantage of voltage closed-loop regulation is to improve the stability of the output voltage, and the load regulation rate will be significantly better than the way of directly increasing the voltage regulator circuit.
  • the switching transistor Q1 can be a MOSFET.
  • the above six embodiments use a MOSFET for description, and the switching transistor Q1 can also adopt a triode, which belongs to the prior art.
  • An implementation of the Boost boost circuit is not described here.
  • a capacitor C4 (not shown) may be connected between the drain and the source of the switching transistor Q1 or a capacitor C4 (not shown) connected in parallel with the boosting inductor L1 may be added. Or, when a capacitor is connected between the drain and the source of the switching transistor Q1, another capacitor is connected in parallel with the boosting inductor L1, and the soft-starting of the circuit can also be achieved.
  • the working principle is the same as the embodiment of the present invention.
  • the working principle of the third embodiment is the same.
  • the stability of the output circuit can be improved by adding a stable circuit, and will not be described here.
  • the method for increasing the feedback control circuit can also improve the stability of the output circuit, which will not be described herein.

Abstract

一种电源电路，包括Boost升压电路，还包括第二电容（C2）、第三电容（C3）和第二二极管（D2）；第二电容连接在该Boost升压电路中开关管（Q1）和升压电感（L1）的连接点与升压二极管（D1）的阳极之间，该升压二极管的阴极依次通过该Boost升压电路中的输出滤波电容（C1）和第三电容连接到电压参考端，第二二极管的阴极与该升压二极管的阳极相连接，第二二极管的阳极连接到第三电容和该输出滤波电容的连接点。该电源电路生产工艺简单，易于实现低成本、小型化，特别适用于微功率、小功率开关电源场合。

Description

一种电源电路
技术领域
本发明涉及一种电源电路， 特别涉及电容隔离的直流 /直流变换器。 背景技术
目前在开关电源技术中绝大部分都是采用电磁变压器来实现原副边电气隔 离。 电磁变压器通过将两个或两个以上的绕组绕在同一磁芯上， 根据电磁感应原 理实现原副边电压、 电流、 阻抗的变化的同时达到能量传输的目的。 电磁变压器 具有传输功率密度大， 负载调整率好等优点而被普遍应用。
但是电磁变压器的结构决定其加工的自动化水平较低，其生产加工目前还是 属于劳动力密集型。因此对于一些结构极为简单的微功率电源模块， 变压器工艺 及其在产品制程中所占的装配环节耗时过大，使得产品的总成本升高。特别是在 人工成本不断上涨的时代背景下， 降低人工成本成为一个迫切需要解决的问题。
公知地， 电容器能作为电气隔离器件并具有能量传输的作用， 利用电感器与 电容器串联产生谐振能实现输入输出隔离及能量能传输， 申请号为 201010287926.5的中国发明专利公开说明书、 公开号为 CA2141389A1的加拿大 专利说明书以及公开号为 CA2131689A1的加拿大专利说明书中， 均公开了一种 使用电容隔离的电源装置，它们所采用的能量传输方式是:通过半桥或全桥电路， 控制其开关频率，在谐振网络的输入端产生一频率可调的方波信号（主要是为了 实现稳定输出电压而实施频率调节用）来改变谐振网络的阻抗， 从而实现输出电 压的调节。但这种电容隔离方式存在缺点： 这三种电源装置所采用的都是全桥或 半桥形式的拓朴结构， 半桥电路需要 2个开关管， 全桥电路需要 4个开关管， 且 同一桥臂的两个开关管需要隔离驱动，同一桥臂的两个开关管驱动信号间需要人 为地加入死区时间来防止直通现象。这样在器件数量以及控制电路的复杂程度上 都大大增加， 这样在一些微功率和小功率场电源场合显然是一种过设计， 同时难 以实现产品小型化和低成本的要求。
当前， 开关电源的小型化、 高效率依然是其发展方向。对于开关电源的小型 化，提高其工作频率已经被证明是一个行之有效的方法， 但一个最有效的方法就 是减少元器件数量； 而软开关技术是提高变换器效率重要手段。实际上就目前的 应用来讲，对于小功率，特别是微功率电源模块，小体积相对于高效率更加重要。
众所周知， Boost 拓扑为一传统的非隔离式升压电路， 大多应用在中功率 (70W 以上） 到大功率开关电源中作为前级的预稳压调节。 由于该电路在不做 任何改动下只能应用于对输入输出不需要进行隔离的场合，其应用范围受到了一 定的限制。 图 1示出了传统的 Boost升压电路， 包括驱动电路、 升压电感 Ll、 开关管 Ql、 升压二极管 Dl和输出滤波电容 C1 ; 电压输入端 Vin通过升压电感 L1连接到开关管 Q1的漏极， 驱动电路的输出端连接到开关管 Q1的栅极， 开关 管 Q1的源极连接到电压参考端， 其漏极连接到升压二极管 D1的阳极， 升压二 极管 D1的阴极通过输出滤波电容 C1连接到开关管 Q1的源极， 输出滤波电容 C1的两端为电路的输出端， 负载 R接在其间。 值得一提的是， 该输出滤波电容 可以采用电解电容， 也可以采用无极性电容， 若采用电解电容， 此时升压二极管 D1 的阴极要接电解电容的正极。 电路的工作过程如下： 开关管 Q1 导通期间， 升压电感 L1在输入电源的激励下储能， 负载能量由输出滤波电容提供， 开关管 Q1关断期间， 升压电感 L1通过升压二极管 D1向负载提供能量的同时给输出滤 波电容 C1充电， 电路的工作波形如图 2所示。 由电路的工作过程可以得知， 该 传统的 Boost电路拓扑只能用于升压变换， 也就是说， 输出电压必然大于输入电 压。 该传统的 Boost升压电路中的开关管可以采用 MOSFET或三极管实现， 上 述以 MOSFET作说明， 三极管的实现原理与之相同， 不再赘述。 发明内容
本发明的目的是提供一种电源电路， 它能解决上述问题， 通过简单的电路结 构实现电源电路原副边的电容隔离传输。
本发明的目的是通过以下技术措施来实现的：
一种电源电路， 包括 Boost升压电路， 还包括第二电容、 第三电容和第二二 极管； 第二电容连接在所述 Boost升压电路中开关管和升压电感的连接点与所述 升压二极管的阳极之间，所述升压二极管的阴极依次通过所述 Boost升压电路中 的输出滤波电容和第三电容连接到电压参考端，第二二极管的阴极与所述升压二 极管的阳极相连接，第二二极管的阳极连接到第三电容和所述输出滤波电容的连 接点。
更优的，还包括第四电容； 第四电容连接在所述开关管和升压电感的连接点 与电压参考端之间。
更优的， 还包括第五电容； 第五电容与所述升压电感相并联。
更优的，还包括第四电容和第五电容； 第四电容连接在所述开关管和升压电 感的连接点与电压参考端之间； 第五电容与所述升压电感相并联。
为了提高电路开环时输出电压的稳定性，还包括稳压电路； 稳压电路连接在 所述输出滤波电容和负载之间。
为了在负载或输入电压扰动时输出稳定电压，还包括反馈控制电路； 反馈控 制电路连接在所述 Boost升压电路的输出端和驱动电路之间。
本发明的目的还可通过以下技术措施实现：
一种电源电路， 包括 Boost升压电路， 还包括第二电容、 第三电容、 第四二 极管、 第五二极管和第六二极管； 第二电容连接在所述 Boost升压电路中开关管 和升压电感的连接点与所述升压二极管的阳极之间，所述升压二极管的阴极依次 通过所述 Boost升压电路中的输出滤波电容、第六二极管和第三电容连接到电压 参考端，其中第六二极管的阴极与第三电容相连接， 第四二极管的阴极与所述升 压二极管的阴极相连接，其阳极连接到第六二极管的阴极， 第五二极管的阴极连 接到所述升压二极管的阳极， 其阳极连接到第六二极管的阳极。
更优的，还包括第四电容； 第四电容连接在所述开关管和升压电感的连接点 与电压参考端之间。
更优的， 还包括第五电容； 第五电容与所述升压电感相并联。
更优的，还包括第四电容和第五电容； 第四电容连接在所述开关管和升压电 感的连接点与电压参考端之间； 第五电容与所述升压电感相并联。
与现有技术相比， 本发明具有以下有益效果：
本发明使用电容耦合传输能量，取代了传统的变压器传输， 实现了电路原副 边的电气隔离， 同时， 本发明只需采用单开关管以及单电感， 配合原副边的隔离 电容即可实现能量的传递，克服以往开关电源采用电磁变压器进行隔离时的工艺 复杂， 人力成本高等问题， 以及以往电容隔离方案中采用半桥或全桥电路的电路 复杂， 成本高， 不易小型化等问题， 所以， 本发明简化了产品的生产工艺， 大大 节约了人工成本， 具有易于实现低成本、 小型化， 特别适用于微功率、 小功率开 关电源场合的特点。 附图说明
下面结合附图和具体实施例对本发明作进一步的详细说明。
图 1为传统的 Boost升压电路的电路原理图；
图 2为 Boost升压电路工作时的波形图；
图 3为本发明实施例一的演化电路图之一；
图 4为本发明实施例一的演化电路图之二；
图 5为图 4所示电路的工作波形图；
图 6为本发明实施例一的电路原理图；
图 7为本发明实施例二的电路原理图；
图 8为本发明实施例二的工作波形图；
图 9为本发明实施例三的电路原理图；
图 10为本发明实施例四的电路原理图；
图 11为本发明实施例五的电路原理图；
图 12为本发明实施例六的电路原理图； 具体实施方式
实施例一
图 6示出了本发明实施例一的电源电路， 包括 Boost升压电路、 电容 C2、 二极管 D2和电容 C3; Boost升压电路的连接方式与图 1所示电路相同， 开关管 Q1的漏极通过电容 C2连接到升压二极管 D1的阳极， 二极管 D1的阴极依次通 过输出滤波电容 C1与电容 C3连接到电压参考端， 输出滤波电容 C1和电容 C3 的连接点与二极管 D2的阳极相连接， 二极管 D2的阴极连接到升压二极管 D1 的阳极。
下面基于传统的 Boost升压电路 （如图 1 ) 逐步增加本发明实施例一中的电 容 C2、 二极管 D2和电容 C3， 通过图 3和图 5所示电路说明本发明基于传统的 Boost 升压电路如何一步步演变成为本发明实施例一的电容隔离型单管直流 /直 流变换器， 在仅采用单个开关管， 单个电感配合隔离电容的情况下， 实现了原副 边隔离的同时达到传递能量的目的。
需要说明的是， 本发明与 Boost升压电路有本质的区别， Boost电路只能用 于升压， 而本发明不但可以升压， 还可以降压， 是一种全新的拓扑结构， 为了便 于本领域技术人员理解电路工作原理， 才在此借 Boost升压电路逐步演变说明。
如图 3所示， 在传统 Boost升压电路的基础上， 在二极管 D1的阳极与开关 管 Q1的漏极之间串联电容 C2。 在开关管 Ql导通期间， 由于二极管 D1的单向 导电性， 电容 C2上的电荷因二极管 D1的单向导电性， 没有放电回路， 因此图 1所示电路不能正常工作。
如图 4所示， 在图 3所示电路的基础上， 在二极管 D1的阳极与开关管 Q1 的源极之间串接二极管 D2， 二极管 D2的阴极与二极管 D1的阳极相连接， 二极 管 D2的阳极与开关管 Q1的源极相连接。 在开关管 Q1导通期间， 电容 C2存在 放电回路， 图 4所示电路可以正常工作， 由于电容 C2的分压作用， 该电路不仅 可以实现升压， 参数设计合理， 同样可以实现降压， 电路的工作原理为： 开关管 Q1导通期间，升压电感 L1在输入电源的激励下储能， 负载能量由输出滤波电容 C1提供。 开关管 Q1关断期间， 升压电感 L1通过电容 C2、 二极管 D1向负载 R 提供能量的同时给输出滤波电容 C1充电，在此期间， B点的电压由于二极管 D1 的导通被箝位在输出电压， A点电压由于电容 C2中一直有同一方向的电流流过， 因此其电压在升压电感 L1 电流下降到零时达到峰值， 之后由于升压电感 L1中 的能量已释放完毕， 二极管 D1关断， B点的电压被二极管 D2箝位， 同时拉低 A点的电位， 当 A点电位与输入电压相等时， 电感 Ll、 电容 C2经二极管 D2， 输入电源形成谐振， 由于输入电源可以看做为一个大电容， 因此 A点电位缓慢 变化， 直到开关管 Q1再次导通， 破坏谐振条件， 电容 C2中的储能通过开关管 Q1和二极管 D2形成的放电回路放电， 电容 C2上存储的能量复位， 接着开始下 一个工作周期， 图 4所示电路的工作波形如图 5所示。
图 6示出的本发明实施例一的电源电路，在图 4所示电路的基础上， 在二极 管 D2阳极和输出滤波电容 C1的连接点与开关管 Q1的源极之间串接电容 C3。 电容 C2和电容 C3形成了电源电路原边侧 （输入侧） 和副边侧 （输出侧） 的电 气隔离， 图中的虚线即为隔离点， 虚线的左边相当于原边侧 （输入侧）， 右边相 当于副边侧 （输出侧）。 从电路的角度， 把二极管 Dl、 二极管 D2、 输出滤波电 容 C1以及电路的负载等效为一个等效负载， 那么电容 C2、 电容 C3和等效负载 组成一串联电路， 因此可以把电容 C2和电容 C3等效为一个电容， 因此本发明 实施例一与图 4所示电路的工作原理相同。 实际上， 从整个电路结构分析可知， 在升压电感 L1存储的能量向负载端悉放过程中，整个电压回路所包升压电感 Ll、 电容 C2、 二极管 Dl、 负载 R、 电容 C3及电路的输入电源。 根据基尔霍夫电压 定律可知，输出端负载上的电压值为输入端电源电压与串联回路上所有其它分压 器件的电压之差， 该过程亦可看成是一阻尼振荡过程。 实施例二
图 7示出了本发明实施例二的电源电路，其与本发明实施例一的电路构成和 工作原理基本相同， 不同点在于增加了电容 C4， 电容 C4接在开关管 Q1的源极 和漏极之间； 电容 C4能起到理想的缓冲效果， 改善电路中开关管 Q1的漏极（A 点） 电压波形 （如图 8所示）， 即降低开关管 Q1关断瞬间其漏极 （A点） 电压 的上升速率^ / ，实现电路的软开效果，从而降低了电路的噪声、改善了其 EMC 特性，通过软开关还能减少开关管的损耗， 有利于频率的提高和电源电路产品的 小型化。 从电路结构上看， 电容 C4与电容 C2、 电容 C3和输出等效负载构成的 支路形成并联结构， 因此在其他参数不变的情况下， 增加电容 C4必然会造成输 出功率降低。但近似正弦的开关管 Q1漏极电压波形和开关管 Q1的零电压开通， 可以在大大提高工作频率的同时提高电路的转换效率。 实施例三
图 9示出了本发明实施例三的电源电路，其与本发明实施例二的电路构成和 工作原理基本相同， 不同点在于电容 C4与升压电感 L1相并联。 事实上， 实施 例三与实施例二的工作本质及最终效果是完全一致的。其根本原因在于， 对于高 频信号来讲， 输入电源由于其电位恒定， 可以看成为短路， 因此电容 C1与升压 电感 L1并联和与接在开关管 Q1的漏源极之间无差别。 实施例三与实施例二的 工作波型相同 （如图 8所示）。 实施例四
图 10示出了本发明实施例四的电源电路， 其与本发明实施例一的电路构成 和工作原理基本相同， 不同点在于在电路的输出侧， 用全桥整流电路取代了实施 例一中由二极管 D1和二极管 D2组成的半桥整流电路， 全桥整流电路包括二极 管 D3、 二极管 D4、 二极管 D5和二极管 D6， 二极管 D3的阳极与电容 C2输出 侧的一端相连接， 二极管 D6的阴极与电容 C3输出侧的一端相连接， 二极管 D3 的阴极连接到二极管 D4的阴极， 二极管 D4的阳极连接到二极管 D6的阴极， 二极管 D6的阳极连接到二极管 D5的阳极， 二极管 D5的阴极连接到二极管 D3 的阳极， 电容 C1连接在二极管 D4的阴极和二极管 D6的阳极之间。
从上述对实施例一的分析可知， 本发明的电路能正常工作的一个重要条件 是： 电感 L电流下降为 0后， 电容 C2和电容 C3中存储的能量能够复位。 半桥 整流的好处在于实现输出电压较低的电路方案时能将整流电路所占的损耗比重 降低， 从而提高产品的效率。但同时应注意到的是， 半桥整流的方法使将使得输 出电压的脉动增加。 这将增加滤波电路压力。对于低输出电压的情况， 半桥整流 电路能提升效率， 因此其所带来的负面影响是可以接受的。然而在较高的输出电 压情况下， 整流电路所带来的压降所占的比重下降。桥式整流电路的好处在于能 得到较小的输出电压脉动， 且同样能为电容 C2和电容 C3电容的复位提供放电 回路， 其工作原理与实施例一基本相同。 实施例五
图 11示出了本发明实施例五的电源电路， 其与本发明实施例一的电路构成 和工作原理基本相同， 不同点在于输出滤波电容 C1与负载 R之间增加了稳压电 路。对于开环电路的产品方案， 增加稳压电路是必须的。 这有利提高电路对负载 变化的调节能力。 从而在一定程度上提高输出电压的稳定性。 实施例六
图 12示出了本发明实施例六的电源电路， 其与本发明实施例一的电路构成 和工作原理基本相同， 不同点在于还包括反馈控制电路， 主要包含电压采样， 误 差放大， 隔离耦合， PFM 调节等主要环节， 其连接在电路的输出端和驱动电路 之间， 使得电路成为一种输出电压闭环的结构。
实施例六的工作原理为： 从上述的实施例分析可知， 输出负载电压与谐振时 电路回路中电感与电容器的分压有关。 同时电容对交流信号的阻抗为 ^ 电感 对交流信号的阻抗为^£。 通过调节不同的驱动频率， 使得电感或电容上的分压 改变， 从而达到调节输出电压幅值的目的。 也正是由于这个机理， 本发明才能实 现升、 降压输出。 当输出电压变化时， 通过输出端的分压网络进行电压采样、 采 样电压经与基准电压比较后产生一个误差信号，该信号通过光电耦进行放大并传 输到原边， 并参与 PFM调节电路的控制。 从而起到调节驱动频率的作用。 实现 输出电压的稳定。 电压闭环调节的优点在于提高输出电压的稳定性， 负载调整率 将明显优于直接增加稳压电路的方式。
以上实施例一到实施例六示出的电源电路中， 开关管 Q1可以是 MOSFET, 上面的六个实施例采用了 MOSFET作说明， 而开关管 Q1 同样也可以采用三极 管， 这属于现有技术中 Boost升压电路的一种实现方式， 在此不再赘述。
本发明还可采用其它实施方式， 如在上述实施例一中， 在开关管 Q1的漏源 极之间连接一个电容的同时， 还有另一个电容与升压电感 L1相并联， 同样能达 到使电路软启动的目的， 其工作原理与实施例二和实施三相同， 在此不再赘述。
如在上述实施例四中， 也可以在开关管 Q1 的漏源极之间连接电容 C4 (图 中未示出） 或者增加与升压电感 L1并联的电容 C4 (图中未示出）， 又或者在开 关管 Q1的漏源极之间连接一个电容的同时， 还有另一个电容与升压电感 L1相 并联， 同样能达到使电路软启动的目的， 其工作原理与本发明实施例二和实施例 三的工作原理相同。
如上述实施例二到实施例四中， 同样能够通过增加稳定电路的方法， 达到提 高输出电路稳定性的目的， 在此不再一一说明。
又如上述实施例二到实施例四中， 同样能够通过增加反馈控制电路的方法， 达到提高输出电路稳定性的目的， 在此不再一一说明。
以上仅是本发明的优选实施方式， 应当指出的是， 上述优选实施方式不应视 为对本发明的限制，本发明的保护范围应当以权利要求所限定的范围为准。对于 本技术领域的普通技术人员来说，在不脱离本发明的精神和范围内， 还可以做出 若干改进和润饰， 这些改进和润饰也应视为本发明的保护范围。

Claims

权利要求
1、 一种电源电路， 包括 Boost升压电路， 其特征在于： 还包括第二电容、 第 三电容和第二二极管； 第二电容连接在所述 Boost升压电路中开关管和升压电感 的连接点与所述升压二极管的阳极之间， 所述升压二极管的阴极依次通过所述 Boost升压电路中的输出滤波电容和第三电容连接到电压参考端， 第二二极管的 阴极与所述升压二极管的阳极相连接，第二二极管的阳极连接到第三电容和所述 输出滤波电容的连接点。
2、 根据权利要求 1所述电源电路， 其特征在于： 还包括第四电容； 第四电容 连接在所述开关管和升压电感的连接点与电压参考端之间。
3、 根据权利要求 1所述电源电路， 其特征在于： 还包括第五电容； 第五电容 与所述升压电感相并联。
4、根据权利要求 1所述电源电路，其特征在于：还包括第四电容和第五电容； 第四电容连接在所述开关管和升压电感的连接点与电压参考端之间；第五电容与 所述升压电感相并联。
5、根据权利要求 1~4中任一权利要求所述电源电路， 其特征在于： 还包括稳 压电路； 稳压电路连接在所述输出滤波电容和负载之间。
6、根据权利要求 1~4中任一权利要求所述电源电路， 其特征在于： 还包括反 馈控制电路；反馈控制电路连接在所述 Boost升压电路的输出端和驱动电路之间。
7、 一种电源电路， 包括 Boost升压电路， 其特征在于： 还包括第二电容、 第 三电容、 第四二极管、 第五二极管和第六二极管； 第二电容连接在所述 Boost升 压电路中开关管和升压电感的连接点与所述升压二极管的阳极之间，所述升压二 极管的阴极依次通过所述 Boost升压电路中的输出滤波电容、第六二极管和第三 电容连接到电压参考端，其中第六二极管的阴极与第三电容相连接， 第四二极管 的阴极与所述升压二极管的阴极相连接，其阳极连接到第六二极管的阴极， 第五 二极管的阴极连接到所述升压二极管的阳极， 其阳极连接到第六二极管的阳极。
8、 根据权利要求 7所述电源电路， 其特征在于： 还包括第四电容； 第四电容 连接在所述开关管和升压电感的连接点与电压参考端之间。
9、 根据权利要求 7所述电源电路， 其特征在于： 还包括第五电容； 第五电容 与所述升压电感相并联。
10、 根据权利要求 7所述电源电路， 其特征在于： 还包括第四电容和第五电 容； 第四电容连接在所述开关管和升压电感的连接点与电压参考端之间： 第五电 容与所述升压电感相并联。
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