CN101666823B - Current detection method and device for LLC resonance circuit - Google Patents

Current detection method and device for LLC resonance circuit Download PDF

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CN101666823B
CN101666823B CN 200810215877 CN200810215877A CN101666823B CN 101666823 B CN101666823 B CN 101666823B CN 200810215877 CN200810215877 CN 200810215877 CN 200810215877 A CN200810215877 A CN 200810215877A CN 101666823 B CN101666823 B CN 101666823B
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diode
resonant circuit
resistance
llc resonant
voltage
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CN101666823A (en
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糜晓宇
肖学礼
林清森
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Vertiv Corp
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Liebert Corp
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Abstract

The invention discloses current detection method and device for an LLC resonance circuit, wherein the method comprises the following step: indirectly detecting the current of a resonance loop by detecting the voltage of a resonant capacitor according to a formula of i=C(du/dt), wherein i is the current of the resonance circuit, C is the capacitance value of the resonant capacitor, and u is the voltage of the resonant capacitor. The device comprises a rectifier and a sampling resistor, wherein the rectifier is used for rectifying the voltage on the resonant capacitor, and rectified voltage is sampled by the sampling resistor. The invention does not need two sampling circuits to respectively sample the current of a positive bus and a negative bus, thereby reducing the design cost and havingconvenient control. The invention can indirectly reflect the amount of the current of the resonance loop and effectively detect the current of the resonance loop so as to timely carry out uninterrupted current-limiting protection on a main loop and prevent damaging a main power switch under a limited condition due to overcurrent. Moreover, the invention has simple structure and low cost and can effectively improve product competitiveness.

Description

A kind of electric current detecting method and device for the LLC resonant circuit
Technical field
The present invention relates to a kind of electric current detecting method for the LLC resonant circuit, the invention still further relates to a kind of current sensing means for the LLC resonant circuit.
Background technology
The Switching Power Supply development trend is at present: high frequency small, high power density, high-level efficiency, low cost.And traditional on-off circuit is because semiconductor devices is in the hard switching duty, and its loss is very large, can't improve self efficient, thereby makes bulkyly, loses gradually the market competitiveness.Soft switch circuit topology becomes the selection that product competitiveness improves in most of Switching Power Supply manufacturer, and very many about research and the patent of soft switch circuit aspect, wherein the LLC resonant circuit obtains a lot of Switching Power Supply tradesmans' favor.What LLC resonant circuit transformer secondary connect is double-bus, if sample circuit is placed on secondary, sampled-current has so just increased design cost to the electric current of positive and negative busbar just to need the two-way sample circuit to come respectively, also is disadvantageous concerning control simultaneously.The frequency of operation of LLC resonant circuit higher (more than the 100KHz), and general HF current transformer (CT) and Hall element can not well reflect the size of actual current under high like this frequency, and the circuit design of CT secondary is also complicated.So be undesirable with high frequency CT and Hall element as the element of sample circuit.Usually the LLC resonant circuit is applied in the situation of high pressure (380V) input, low pressure (72V) output, and the transformer secondary connects is single busbar full-wave rectifying circuit structure.So a minute flowmeter is ideal selection very.But in the situation that low pressure (72V) is inputted, high pressure (380V) output, because primary current is large, frequency is high, so a minute flowmeter neither ideal chose.
Summary of the invention
Technical matters to be solved by this invention is exactly in order to overcome above deficiency, to have proposed a kind of electric current detecting method for the LLC resonant circuit and device, and is simple in structure, cost is low.
Technical matters of the present invention is solved by following technical scheme:
A kind of electric current detecting method for the LLC resonant circuit comprises the steps: the electric current by detection resonant capacitance voltage indirect detection resonant tank, i = C du dt , Wherein, i is the electric current of resonant circuit, and C is the appearance value of resonant capacitance; U is resonant capacitance voltage.
Described resonant capacitance voltage is through rectifier rectification.
A kind of current sensing means for the LLC resonant circuit comprises rectifier and sampling resistor, and described rectifier carries out rectification to the voltage on the resonant capacitance, and the voltage after the rectification is sampled by described sampling resistor.
Described rectifier comprises the first diode, the second diode, the 3rd diode, the 4th diode, and described sampling resistor comprises the first resistance and the second resistance; Described the first diode anode links to each other respectively with the 3rd diode anode, the first resistance, described the first diode cathode links to each other respectively with the second diode anode, resonant capacitance first end, described the second diode cathode links to each other respectively with the 4th diode cathode, the second resistance, and described the 3rd diode cathode links to each other respectively with resonant capacitance the second end, the 4th diode anode.
Described the first diode, the second diode, the 3rd diode, the 4th diode are respectively fast recovery diode or schottky diode.
Described rectifier comprises the first diode, and described sampling resistor comprises the first resistance and the second resistance; Described the first diode anode is connected between the main-transformer of resonant capacitance first end and LLC resonant circuit and links to each other with the resonant capacitance first end, and negative electrode links to each other with the second resistance, and described the first resistance links to each other with resonant capacitance the second end.
Described rectifier comprises the first diode, and described sampling resistor comprises the first resistance and the second resistance; Described the first diode anode is connected between the primary power switch device of resonant capacitance the second end and LLC resonant circuit, and negative electrode links to each other with the first resistance, and described the second resistance links to each other with the resonant capacitance first end.
Described the first diode is fast recovery diode or schottky diode.
What the transformer secondary of described LLC resonant circuit connect is double-bus.
The beneficial effect that the present invention is compared with the prior art is: the present invention does not need to come respectively with the two-way sample circuit, and sampled-current has reduced design cost to the electric current of positive and negative busbar, and convenient control.By the present invention; the size that can indirectly reflect resonant tank current; effectively detect resonant tank current; thereby in time to carrying out the wave limiting protection during the major loop; prevent in limiting condition because overcurrent damages the master power switch pipe, but and the present invention is simple in structure, the low Effective Raise product competitiveness of cost.
Description of drawings
Fig. 1 is the structural representation of the specific embodiment of the invention one;
Fig. 2 is the structural representation of the specific embodiment of the invention two;
Fig. 3 is the structural representation of the specific embodiment of the invention three.
Embodiment
Also by reference to the accompanying drawings the present invention is described in further details below by concrete embodiment.
Embodiment one
As shown in Figure 1, a kind of LLC resonant circuit, comprise resonant inductance Lr, main-transformer T, resonant capacitance Cr, primary power switch device Q201, Q202, Q203, Q204, secondary power fast recovery diode D271, D272, D273, D274, described LLC resonant circuit is connected to DC input voitage Ui.Described primary power switch device Q201, Q202, Q203, Q204 endophyte or add fly-wheel diode and electric capacity.What the transformer secondary of described LLC resonant circuit connect is double-bus, is respectively positive bus-bar BUSS+ and negative busbar BUSS-.
This LLC resonant circuit is can realize that by the switching frequency of control primary power switch device Q201, Q202, Q203, Q204 the no-voltage of primary power switch device Q201, Q202, Q203, Q204 opens the zero-current switching of (ZVS) and secondary diode (ZCS), so just can corresponding raising primary power switch device Q201, the frequency of operation of Q202, Q203, Q204, be conducive to the design of magnetic element and the raising of overall efficiency.For the device in the main topological circuit is made overcurrent protection and current detecting, this just need to detect the electric current in the main topological circuit.
Current sensing means for the LLC resonant circuit of the present invention comprises rectifier and sampling resistor, and described rectifier carries out rectification to the voltage on the resonant capacitance, and the voltage after the rectification is sampled by described sampling resistor.The present invention does not need to come respectively with the two-way sample circuit, and sampled-current has reduced design cost to the electric current of positive and negative busbar, and convenient control.
Described rectifier comprises the first diode D1, the second diode D2, the 3rd diode D3, the 4th diode D4, and described sampling resistor comprises the first resistance R 1 and the second resistance R 2.Described the first diode D1 anode links to each other respectively with the 3rd diode D3 anode, the first resistance R 1, described the first diode D1 negative electrode links to each other respectively with the second diode D2 anode, resonant capacitance Cr first end, described the second diode D2 negative electrode links to each other respectively with the 4th diode D4 negative electrode, the second resistance R 2, and described the 3rd diode D3 negative electrode links to each other respectively with resonant capacitance Cr the second end, the 4th diode D4 anode.
The first diode D1, the second diode D2, the 3rd diode D3 and the 4th diode D4 are fast recovery diode or schottky diode respectively.
In the work of LLC resonant circuit, the resonance current in the resonant tank and resonant capacitance voltage have close contacting.When the resonance current in the resonant tank became large, it is large that resonant capacitance voltage also becomes thereupon, and vice versa.The voltage waveform at resonant capacitance two ends is the sine waves with the switching frequency same frequency, and the resonance current waveform is with sinusoidal wave approximate.
The relation of resonance current and resonant capacitance voltage is as follows: resonance current: i = C du dt , Wherein, i is the electric current of resonant circuit, and C is the appearance value of resonant capacitance; U is resonant capacitance voltage.
The resonance current effective value: I = ∫ 0 π ( C × d ( U max sin ( ωt ) ) dt ) 2 · dωt π
Power input: P = U in × I = U in × ∫ 0 π ( C × d ( U max sin ( ωt ) ) dt ) 2 · dωt π
Wherein: U MaxBe the resonant capacitance voltage max; ω=2 π f; Uin is input voltage.
Can obtain the funtcional relationship of resonance current and resonant capacitance voltage and power input and resonant capacitance voltage from above-mentioned derivation, namely the size by resonant capacitance voltage reflects the size of resonance current and the size of power input.So we can come the indirect detection resonance current by detecting resonant capacitance voltage.Because resonant capacitance voltage is the high-frequency ac value, conveniently detect usefulness so need to become the direct current effective value to it, so with rectifier resonant capacitance voltage is carried out rectification, the magnitude of voltage after the rectification can reflect resonant capacitance voltage.Just can judge the size of resonance current by the magnitude of voltage after the rectification.Detection of the present invention is effective.
By the present invention; the size that can indirectly reflect resonant tank current; effectively detect resonant tank current; thereby in time to carrying out the wave limiting protection during the major loop; prevent in limiting condition because overcurrent damages the master power switch pipe, but and the present invention is simple in structure, the low Effective Raise product competitiveness of cost.
Embodiment two
As shown in Figure 2, this embodiment is with the difference of embodiment one: described rectifier comprises the first diode D1, and described sampling resistor comprises the first resistance R 1 and the second resistance R 2; Described the first diode D1 anodic bonding resonant capacitance Cr first end and LLC resonant circuit main-transformer T between, negative electrode links to each other with the second resistance R 2, described the first resistance R 1 links to each other with resonant capacitance Cr the second end.
Described the first diode D1 is fast recovery diode or schottky diode.
Embodiment three
As shown in Figure 3, this embodiment is with the difference of embodiment one: described rectifier comprises the first diode D1, and described sampling resistor comprises the first resistance R 1 and the second resistance R 2; Described the first diode D1 anodic bonding is between the main primary power switch device of resonant capacitance the second end and LLC resonant circuit, and negative electrode links to each other with the first resistance R 1, and described the second resistance R 2 links to each other with resonant capacitance Cr first end.
Described the first diode D1 is fast recovery diode or schottky diode.
A kind of electric current detecting method for the LLC resonant circuit comprises the steps: the electric current by detection resonant capacitance voltage indirect detection resonant tank, i = C du dt , Wherein, i is the electric current of resonant circuit, and C is the appearance value of resonant capacitance; U is resonant capacitance voltage.Described resonant capacitance voltage is through rectifier rectification.
Above content is in conjunction with concrete preferred implementation further description made for the present invention, can not assert that implementation of the present invention is confined to these explanations.For the general technical staff of the technical field of the invention, without departing from the inventive concept of the premise, can also make some simple deduction or replace, all should be considered as belonging to protection scope of the present invention.

Claims (9)

1. electric current detecting method that is used for the LLC resonant circuit is characterized in that: comprises the steps: by detecting the electric current of the described LLC resonant circuit of resonant capacitance voltage indirect detection,
Figure FDA00002056007800011
Wherein, i is the electric current of described LLC resonant circuit, and C is the appearance value of resonant capacitance; U is resonant capacitance voltage; The effective value of the electric current by detecting the described LLC resonant circuit of described resonant capacitance voltage max indirect detection: I = ∫ 0 π ( C × d ( U max sin ( ωt ) ) dt ) 2 · dωt π , Wherein, U MaxBe the resonant capacitance voltage max; ω=2 π f; F is the switching frequency of described LLC resonant circuit.
2. the electric current detecting method for the LLC resonant circuit according to claim 1, it is characterized in that: described resonant capacitance voltage is through rectifier rectification.
3. current sensing means that is used for the LLC resonant circuit, it is characterized in that: comprise rectifier and sampling resistor, described rectifier carries out rectification to the voltage on the resonant capacitance, and the voltage after the rectification is sampled by described sampling resistor; Judge the size of the electric current of described LLC resonant circuit by the voltage after the described rectification, be specially: I = ∫ 0 π ( C × d ( U max sin ( ωt ) ) dt ) 2 · dωt π , Wherein, I is the effective value of the electric current of described LLC resonant circuit, and C is the appearance value of resonant capacitance, U MaxBe the resonant capacitance voltage max; ω=2 π f; F is the switching frequency of described LLC resonant circuit.
4. the current sensing means for the LLC resonant circuit according to claim 3, it is characterized in that: described rectifier comprises the first diode, the second diode, the 3rd diode, the 4th diode, and described sampling resistor comprises the first resistance and the second resistance; Described the first diode anode links to each other respectively with the 3rd diode anode, the first resistance, described the first diode cathode links to each other respectively with the second diode anode, resonant capacitance first end, described the second diode cathode links to each other respectively with the 4th diode cathode, the second resistance, and described the 3rd diode cathode links to each other respectively with resonant capacitance the second end, the 4th diode anode.
5. the current sensing means for the LLC resonant circuit according to claim 4, it is characterized in that: described the first diode, the second diode, the 3rd diode, the 4th diode are respectively fast recovery diode or schottky diode.
6. the current sensing means for the LLC resonant circuit according to claim 3, it is characterized in that: described rectifier comprises the first diode, described sampling resistor comprises the first resistance and the second resistance; Described the first diode anode is connected between the main-transformer of resonant capacitance first end and LLC resonant circuit, and negative electrode links to each other with the second resistance, and described the first resistance links to each other with resonant capacitance the second end.
7. the current sensing means for the LLC resonant circuit according to claim 3, it is characterized in that: described rectifier comprises the first diode, described sampling resistor comprises the first resistance and the second resistance; Described the first diode anode is connected between the primary power switch device of resonant capacitance the second end and LLC resonant circuit, and negative electrode links to each other with the first resistance, and described the second resistance links to each other with the resonant capacitance first end.
8. according to claim 6 or 7 described current sensing meanss for the LLC resonant circuit, it is characterized in that: described the first diode is fast recovery diode or schottky diode.
9. each described current sensing means for the LLC resonant circuit according to claim 3-7, it is characterized in that: what the transformer secondary of described LLC resonant circuit connect is double-bus.
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CN103138590B (en) * 2011-12-02 2017-02-08 中兴通讯股份有限公司 Current-limiting protection method and device of resonance circuit
CN106059274A (en) * 2016-07-15 2016-10-26 东莞市米町源电子科技有限公司 Resonant control circuit
CN108390569A (en) * 2018-02-06 2018-08-10 福建睿能科技股份有限公司 A kind of power circuit of the symmetrical generating positive and negative voltage of output
CN112083213A (en) * 2020-08-10 2020-12-15 广州金升阳科技有限公司 Converter, current detection circuit and current detection method
CN112134463B (en) * 2020-08-31 2022-06-03 杭州中恒电气股份有限公司 Full-bridge LLC resonant converter and resonant current detection method thereof
CN116848772A (en) * 2021-02-20 2023-10-03 华为技术有限公司 LLC converter, control circuit, soft start method, device and chip
CN117420348A (en) * 2023-12-19 2024-01-19 江苏巧思科技有限公司 Resonant current detection circuit

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CN1407344A (en) * 2001-09-10 2003-04-02 管政有 Current change rate meter
CN1750375A (en) * 2005-08-11 2006-03-22 浙江大学 Resonant current transformer with secondary element device voltage stress is half of output voltage

Patent Citations (3)

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Publication number Priority date Publication date Assignee Title
CN1368787A (en) * 2001-02-09 2002-09-11 台达电子工业股份有限公司 DC/DC converter with LLC serial resonance
CN1407344A (en) * 2001-09-10 2003-04-02 管政有 Current change rate meter
CN1750375A (en) * 2005-08-11 2006-03-22 浙江大学 Resonant current transformer with secondary element device voltage stress is half of output voltage

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