CN100547428C - Be used to detect the method and apparatus of the erasing time of magnetic devices - Google Patents

Abstract

The invention provides a kind of testing circuit that is used to detect the erasing time of magnetic devices.Input circuit is coupled to magnetic devices so that detect the magnetization voltage and the degauss voltage of magnetic devices.Control circuit is coupled to described input circuit so that produce the erasing time signal according to magnetization voltage, degauss voltage and magnetizing time.Magnetizing time is relevant with the cycle of enabling of magnetization voltage.The erasing time of magnetic devices is by the erasing time signal indication.

Description

Be used to detect the method and apparatus of the erasing time of magnetic devices

Technical field

The present invention relates generally to a kind of magnetic devices, and more particularly relates to the control to magnetic devices.

Background technology

Magnetic devices is widely used in provides energy storage, energy to shift and/or signal filtering in the power converter.The energy that stores in the magnetic devices must discharge (demagnetization) before in charging (magnetization) next time, otherwise magnetic saturation will take place.When with voltage V _CWhen being applied to magnetic devices, charging current I _CFlow to magnetic devices.Discharge current I _DAccording to the voltage V on the magnetic devices _DAnd flow out from magnetic devices.I _CAnd I _DCan represent by following equation:

$I_C=\frac{V_C}{L}\×T_{\mathrm{CHARGE}}---\left(1\right)$

$I_D=\frac{V_D}{L}\×T_{\mathrm{DISCHARGE}}---\left(2\right)$

Wherein L is the inductance of magnetic devices, T _CHARGEBe the duration of charging, and T _DISCHARGEIt is discharge time.

Illustrate charging current I among Fig. 1 and Fig. 2 _CWith discharge current I _DFig. 1 illustrates in discontinuous current-mode (Discontinuous current mode, the DCM) electric current of the magnetic devices of operating down, the wherein energy of magnetic devices discharge fully before charging next time.Fig. 2 illustrates the continuous current pattern, and (wherein when next charge cycle had begun, magnetic devices still kept energy for continuouscurrent mode, CCM) operation.DCM and CCM each in the different manifestations that causes current loop aspect the power controlling converter, for example described in the United States Patent (USP) 5,903,452 of Yang " Adaptive slope compensator for currentmode power converters ".Therefore, measuring the discharge time of magnetic devices is key factor for the control of optimized power converter.The usual method that detects discharge time is by using current sensing device to come the switch current of sensing magnetic devices.Yet the sensing of switch current can produce power loss and increase the complicacy of testing circuit.

Summary of the invention

The object of the present invention is to provide a kind of higher and more simple testing circuit of design of efficient that is used to measure the discharge time of magnetic devices.

The invention provides a kind of method and apparatus in order to discharge time of detecting magnetic devices.It comprises input circuit, and described input circuit is coupled to magnetic devices so that detect first voltage and second voltage of magnetic devices.Input circuit further produces first signal, secondary signal and duration of charging signal according to first voltage and second voltage.First voltage is to be applied to magnetic devices to be used for voltage that magnetic devices is charged.Second voltage is the voltage on the interdischarge interval magnetic devices of magnetic devices.Control circuit is coupled to input circuit so that produce discharge time signal according to first signal, secondary signal and duration of charging signal.First signal is relevant with first voltage.Secondary signal is relevant with second voltage.The duration of charging signal is relevant with the cycle of enabling of first voltage.The cycle of discharge time signal is represented the discharge time of magnetic devices.

Description of drawings

Accompanying drawing is used to provide further understanding of the present invention, and incorporates in this instructions and form the part of this instructions.The description of drawings embodiments of the invention, and be used for explaining principle of the present invention with embodiment.In the accompanying drawing,

Fig. 1 illustrates the switch current of the magnetic devices of operating down at discontinuous current-mode (DCM).

Fig. 2 illustrates continuous current pattern (CCM) operation of magnetic devices.

Fig. 3 explanation has the power converter of the testing circuit of the erasing time that is used to detect magnetic devices according to the preferred embodiment of the present invention.

Fig. 4 illustrates the preferred embodiment according to the testing circuit of the embodiment of the invention.

Fig. 5 illustrates the power converter of testing circuit that having of according to the present invention another preferred embodiment is used to detect the erasing time of magnetic devices.

Fig. 6 illustrates the testing circuit of another preferred embodiment according to the present invention.

Fig. 7 illustrates input circuit according to the preferred embodiment of the invention.

Embodiment

Fig. 3 explanation has the power converter of the testing circuit 100 of the discharge time that is used to detect magnetic devices according to the preferred embodiment of the invention, and testing circuit 100 has the first voltage node V1, the second voltage node V2 and ground connection node GND.Testing circuit 100 through coupling so that detect a plurality of voltages of transformer 10.When with voltage source V _EWhen being applied to the main winding of transformer 10, diode 20 is a reverse biased, and transformer 10 is charged.Inferior winding place at the transformer 10 with first node N1 and Section Point N2 produces and voltage source V _EProportional voltage V _INIn addition, the first voltage node V1 of testing circuit is connected to magnetic devices (the second voltage node V2 of for example, the inferior winding of transformer 10) first node N1, and testing circuit 100 is connected to the Section Point N2 of magnetic devices.In case switch 15 cuts out, then produce discharge current I _MOpen diode 20.Simultaneously, as discharge current I _MWhen flowing in the load 30, with voltage V _OAdd the inferior winding of transformer 10 to.

The boundary condition of CCM and DCM is provided by following formula

Φ _C＝Φ _D (3)

$\mathrm{\Φ}=B\×A=\frac{V\×T}{N}---\left(4\right)$

$\frac{V_{\mathrm{IN}}}{N}\×T_{\mathrm{CHARGE}}=\frac{V_O}{N}\×T_{\mathrm{DISCHARGE}}---\left(5\right)$

V _IN×T _CHARGE＝V _O×T _DISCHARGE (6)

Φ wherein _CAnd Φ _DBe respectively the charging flux and the discharge flux of magnetic devices; B is a flux density; A is the cross-sectional area of magnetic devices; T is a cycle of magnetization; N is the umber of turn of magnetic devices; T _CHARGEAnd T _DISCHARGEIt is respectively duration of charging (magnetizing time) and discharge time (erasing time).

(T discharge time of transformer 10 _DISCHARGE) can obtain according to equation (7).

$T_{\mathrm{DISCHARGE}}=\frac{V_{\mathrm{IN}}}{V_O}\×T_{\mathrm{CHARGE}}---\left(7\right)$

Equation (7) illustrates can be according to voltage V _IN, voltage V _OWith duration of charging T _CHARGEDetect T discharge time _DISCHARGE

Fig. 4 illustrates testing circuit 100 according to the preferred embodiment of the invention.Input circuit 105 is coupled to magnetic devices (for example, transformer 10) to detect the first voltage V ₁With the second voltage V ₂Thereby, according to the first voltage V ₁With the second voltage V ₂Produce the first signal I ₁, secondary signal I ₂With duration of charging signal V _SThe first voltage V ₁Be to be applied to magnetic devices to be used for voltage (for example, voltage V that magnetic devices is charged _IN).The second voltage V ₂Be voltage (for example, the voltage V on magnetic devices during the discharge cycle of magnetic devices _O).The first voltage V ₁Therefore expression magnetization voltage, and the second voltage V ₂The expression degauss voltage.

Control circuit 195 is coupled to input circuit 105 so that according to the first signal I ₁, secondary signal I ₂With duration of charging signal V _SProduce discharge time signal S _DThe first signal I ₁With the first voltage V ₁Relevant.Secondary signal I ₂With the second voltage V ₂Relevant.Duration of charging signal V _SWith the first voltage V ₁The cycle of enabling relevant.Therefore, discharge time signal S _DCycle represent discharge time of magnetic devices, wherein discharge time signal S _DCycle according to the first voltage V ₁Increase and increase.Discharge time signal S _DCycle according to duration of charging signal V _SReducing of cycle and reduce.In addition, discharge time signal S _DCycle according to the second voltage V ₂Increase and reduce.

Control circuit 195 comprises capacitor 150.Switch 110 is coupling in the first signal I ₁And between the capacitor 150.Switch 120 is coupling in secondary signal I ₂And between the capacitor 150.Comparer 160 is coupled to capacitor 150, in case so that the voltage of capacitor 150 is higher than reference voltage V _ZThen produce switching signal.Switching signal is connected to the input end of AND door 175.Another input end of AND door 175 is coupled to duration of charging signal V by phase inverter 172 and buffer circuits 171 _SAND door 175 is operated so that according to switching signal and duration of charging signal V as output circuit _SForbidding and produce discharge time signal S _DSwitch 110 is according to duration of charging signal V _SEnable and open.Switch 120 is according to discharge time signal S _DEnable and open.So first signal I ₁Be used for capacitor 150 is charged, and secondary signal I ₂Be used for capacitor 150 is discharged.

Fig. 5 illustrates another preferred embodiment of the power converter of the testing circuit 200 with the erasing time that is used to detect magnetic devices.Testing circuit 200 through coupling so that detect the voltage of inductor 50.When switch 45 was opened, diode 60 was closed.May apply differential voltage (V at the moment _IN-V _O) come inductor 50 is charged.In case switch 45 cuts out, discharge current I then _MBe recycled to diode 60 and load 70.Simultaneously, with voltage V _OAdd inductor 50 to.

The CCM of the power converter shown in Fig. 5 and the boundary condition of DCM are provided by following formula

(V _IN-V _O)×T _CHARGE＝V _O×T _DISCHARGE (7)

$T_{\mathrm{DISCHARGE}}=\frac{(V_{\mathrm{IN}}-V_O)}{V_O}\×T_{\mathrm{CHARGE}}---\left(8\right)$

Above equation (8) illustrates can be according to voltage V _IN, voltage V _OWith duration of charging T _CHARGEDetect T discharge time _DISCHARGE

Fig. 6 illustrates the preferred embodiment of testing circuit 200.Illustrate at least one ground connection node in the testing circuit 200 of Fig. 6.Input circuit 205 is coupled to magnetic devices (inductor 50) to detect the first voltage V at the first voltage node V1 place ₁The second voltage V with the second voltage node V2 place ₂Thereby, according to the first voltage V ₁With the second voltage V ₂Produce the first signal I ₁, secondary signal I ₂, the 3rd signal I ₃With duration of charging signal V _SControl circuit 295 is coupled to input circuit 205 so that according to the first signal I ₁, secondary signal I ₂, the 3rd signal I ₃With duration of charging signal V _SProduce discharge time signal S _DThe 3rd signal I ₃With the second voltage V ₂ Relevant.Control circuit 295 comprises capacitor 250.The first signal I ₁With the 3rd signal I ₃Be connected in series.Switch 210 is coupled to the first signal I ₁With the 3rd signal I ₃Switch 210 further is coupled to capacitor 250.Switch 220 is connected secondary signal I ₂And between the capacitor 250.Comparer 260 is coupled to capacitor 250, in case so that the voltage of capacitor 250 is higher than reference voltage V _ZThen produce and enable signal.Enable the input end that signal is connected to AND door 275.Another input end of AND door 275 is coupled to duration of charging signal V by phase inverter 272 and buffer circuits 271 _SAND door 275 is operated so that in response to enabling signal and duration of charging signal V as output circuit _SForbidding and produce discharge time signal S _DSwitch 210 is according to duration of charging signal V _SEnable and open.Switch 220 is according to discharge time signal S _DEnable and open.The first signal I ₁Deduct the 3rd signal I ₃Be used for differential signal that capacitor 250 is charged with generation.Secondary signal I ₂Through being coupled so that capacitor 250 is discharged.

Fig. 7 illustrates the preferred embodiment of input circuit.It comprises first circuit and second circuit.First resistance device 350 is used to produce the first voltage V of first electric current with detection through coupling ₁A plurality of transistors 360,361,371,372,373 and current source 380 form first circuit.Transistor 360 is coupled to first resistance device 350 with received current I ₃₅₀According to electric current I ₃₅₀, transistor 361 mirrors are coupled to the electric current I of transistor 371 ₃₆₁ Transistor 372 is according to electric current I ₃₆₁Come the mirror electric current I ₃₇₂In addition, transistor 373 is according to electric current I ₃₆₁Produce the first signal I ₁Electric current I ₃₇₂Be connected to current source 380 with convenient electric current I ₃₇₂Produce duration of charging signal V when being higher than the electric current of current source 380 _STherefore, the first signal I ₁With the first voltage V ₁Relevant.Duration of charging signal V _SRepresent the first voltage V ₁Enable the cycle.

Operational amplifier 320, a plurality of resistance device 310,311,321 and a plurality of transistor 324,325,326,327,328 form second circuit.Resistance device 310 and 311 is through being coupled to detect the second voltage V ₂The input end of operational amplifier 320 is connected to resistance device 310 and 311.Operational amplifier 320, resistance device 321 and transistor 323 form converter so that according to the second voltage V ₂And the generation electric current I ₃₂₃Transistor 324 is through being coupled with received current I ₃₂₃And the electric current I at mirrors transistor 325 places ₃₂₅Transistor 326,327 and 328 forms current mirror so that according to electric current I ₃₂₅And generation secondary signal I ₂With the 3rd signal I ₃Therefore, secondary signal I ₂With the 3rd signal I ₃With the second voltage V ₂Relevant.

The first voltage V ₁With the second voltage V ₂Determine the charging current I of capacitor 250 among Fig. 6 _CCharging current I _CCan be expressed as,

$I_C=(k1\×\frac{V1}{R_{350}})-(k3\×\frac{V2}{R_{321}})---\left(9\right)$

The second voltage V ₂Determine the discharge current I of capacitor 250 _DIt is expressed as,

$I_D=k2\×\frac{V2}{R_{321}}---\left(10\right)$

Voltage on the capacitor 250 can be expressed as,

$V_H=\frac{I_C}{C}\×T_{\mathrm{ON}}=\frac{\frac{k1\×V1}{R_{350}}-\frac{k3\×V2}{R_{321}}}{C}\×T_{\mathrm{ON}}---\left(11\right)$

Wherein k1, k2 and k3 are constants, for example the gain of the ratio of resistance device and/or current mirror; C is the electric capacity of capacitor 250; T _ONIt is the duration of charging of capacitor 250.By selecting k1/R ₃₅₀, k3/R ₃₂₁And k2/R ₃₂₁Value be 1/R, equation (11) can be rewritten as,

$V_H=\frac{V1-V2}{R\×C}\×T_{\mathrm{ON}}---\left(12\right)$

T discharge time of capacitor 250 _OFFProvide by following formula,

$T_{\mathrm{OFF}}=\frac{C\×V_H}{I_D}=\frac{C\×V_H}{\frac{V2}{R}}---\left(13\right)$

According to equation (12) and (13), T discharge time of capacitor 250 _OFFT discharge time that can be used as inductor 50 _DISCHARGE

$T_{\mathrm{OFF}}=\frac{V1-V2}{V2}\×T_{\mathrm{ON}}---\left(14\right)$

$T_{\mathrm{DISCHARGE}}=\frac{V1-V2}{V2}\×T_{\mathrm{CHARGE}}---\left(15\right)$

The first voltage V wherein ₁With voltage V _INRelevant; And the second voltage V ₂With voltage V _ORelevant.

Therefore, discharge time signal S _DThe cycle of enabling increase according to the increase of magnetization voltage and cycle of magnetization.In addition, discharge time signal S _DThe cycle of enabling reduce according to the increase of degauss voltage.

Though illustrate and described the present invention with reference to the preferred embodiments of the present invention are specific, but those of ordinary skill in the field will understand, in the various variations that can make therein under the situation that does not break away from the spirit and scope of the invention that is defined by appended claims on form and the details.

Claims (15)

1. testing circuit that is used to detect the discharge time of magnetic devices, it comprises:

Input circuit, it is coupled to described magnetic devices so that detect first voltage and second voltage of described magnetic devices, thereby produce first signal, secondary signal and duration of charging signal according to described first voltage and described second voltage, wherein said first voltage is applied to described magnetic devices and is used for described magnetic devices is charged, and described second voltage is applied on the described magnetic devices at the interdischarge interval of described magnetic devices; And

Control circuit, it is coupled to described input circuit so that produce discharge time signal according to described first signal, described secondary signal and described duration of charging signal,

Wherein said first signal is relevant with described first voltage, described secondary signal is relevant with described second voltage, described duration of charging signal is relevant with the cycle of enabling of described first voltage, and the cycle of described discharge time signal is represented the described discharge time of described magnetic devices.

2. the testing circuit that is used to detect the discharge time of magnetic devices according to claim 1, the increase of the described cycle of wherein said discharge time signal according to described first voltage increases, the described cycle of described discharge time signal reduces according to cycle of described duration of charging signal, and the described cycle of described discharge time signal reduces according to the increase of described second voltage.

3. the testing circuit that is used to detect the discharge time of magnetic devices according to claim 1, wherein said input circuit comprises:

First resistance device, it is used to produce described first voltage of first electric current with detection through coupling;

First circuit, it is coupled to described first resistance device to produce described first signal and described duration of charging signal according to described first electric current; And

Second circuit, it produces second electric current through coupling so that detect described second voltage,

Wherein said secondary signal produces according to described second electric current.

4. the testing circuit that is used to detect the discharge time of magnetic devices according to claim 1, wherein said control circuit comprises:

Capacitor;

First switch, it is coupling between described first signal and the described capacitor;

Second switch, it is coupling between described secondary signal and the described capacitor;

Comparer, it is coupled to described capacitor, in case produce switching signal so that the voltage of described capacitor is higher than reference voltage; And

Output circuit, it produces described discharge time signal through coupling with the forbidding according to described switching signal and described duration of charging signal,

Wherein said first switch is opened according to enabling of described duration of charging signal, described second switch is opened according to enabling of described discharge time signal, described first signal is used for described capacitor is charged, and described secondary signal is used for described capacitor is discharged.

5. testing circuit in order to erasing time of detecting magnetic devices, it comprises:

Input circuit, it is coupled to described magnetic devices so that detect the magnetization voltage and the degauss voltage of described magnetic devices; And

Control circuit, it is coupled to described input circuit so that produce the erasing time signal according to described magnetization voltage, described degauss voltage and magnetizing time, wherein said magnetizing time is relevant with the cycle of enabling of described magnetization voltage, and the described erasing time of the described magnetic devices of described erasing time signal indication.

6. the testing circuit that is used to detect the erasing time of magnetic devices according to claim 5, the increase of the cycle of wherein said erasing time signal according to described magnetization voltage increases, the described cycle of described erasing time signal reduces according to described magnetizing time, and the described cycle of described erasing time signal reduces according to the increase of described degauss voltage.

7. the testing circuit that is used to detect the erasing time of magnetic devices according to claim 5, wherein said input circuit comprises:

First circuit, it is coupled to described magnetization voltage so that produce first signal and magnetizing time signal according to described magnetization voltage, the described magnetizing time of wherein said magnetizing time signal indication; And

Second circuit, it is coupled to described degauss voltage so that produce secondary signal.

8. the testing circuit that is used to detect the erasing time of magnetic devices according to claim 5, wherein said control circuit comprises:

Capacitor;

First switch, it is coupling between described first signal and the described capacitor;

Second switch, it is coupling between described secondary signal and the described capacitor;

Comparer, it is coupled to described capacitor, in case produce switching signal so that the voltage of described capacitor is higher than reference voltage; And

Output circuit, its forbidding according to described switching signal and described magnetizing time signal produces described erasing time signal,

Wherein said first switch enabling according to described magnetizing time signal, described second switch is enabled according to described erasing time signal, described first signal is used for described capacitor is charged, and described secondary signal is used for described capacitor is discharged.

9. equipment that is used to detect the erasing time of magnetic devices, it comprises:

Voltage source;

First switch, it is connected to described voltage source;

Transformer, it has main winding and time winding, and described time winding has first node and Section Point, and described main winding is connected to described first switch;

Testing circuit, it is used to detect the erasing time of described transformer, it has first voltage node, second voltage node and ground connection node, wherein said first voltage node is connected to the described first node of described winding, described second voltage node is connected to the described Section Point of described winding, described ground connection node ground connection, and described testing circuit further comprises:

Input circuit, it is coupled to described transformer so that detect the magnetization voltage and the degauss voltage of described transformer; With

Control circuit, it is coupled to described input circuit so that produce the erasing time signal according to described magnetization voltage, described degauss voltage and magnetizing time, wherein said magnetizing time is relevant with the cycle of enabling of described magnetization voltage, and the described erasing time of the described transformer of described erasing time signal indication;

Diode, it is connected to the described first node and the described ground connection node of described winding; And

Output load, it is connected to the described Section Point and the described ground connection node of described winding.

10. equipment according to claim 9, wherein said input circuit through coupling receiving first voltage and second voltage, thereby obtain discharge time signal to produce duration of charging signal, first signal and secondary signal according to described first voltage and described second voltage.

11. equipment according to claim 10, wherein said control circuit through coupling receiving described duration of charging signal, described first signal and described secondary signal, thereby produce described discharge time signal according to described duration of charging signal, described first signal and described secondary signal.

12. an equipment that is used to detect the erasing time of magnetic devices, it comprises:

Testing circuit, it has first voltage node, second voltage node and ground connection node, wherein said first voltage node is connected to the first node of described magnetic devices, described second voltage node is connected to the Section Point of described magnetic devices, and described ground connection node ground connection, and described testing circuit further comprises:

Input circuit, it is coupled to described magnetic devices so that detect the magnetization voltage and the degauss voltage of described magnetic devices; With

Control circuit, it is coupled to described input circuit so that produce the erasing time signal according to described magnetization voltage, described degauss voltage and magnetizing time, wherein said magnetizing time is relevant with the cycle of enabling of described magnetization voltage, and the described erasing time of the described magnetic devices of described erasing time signal indication; And

Output circuit, it is connected to the described Section Point and the described ground connection node of described magnetic devices.

13. equipment according to claim 12, the described first node of wherein said magnetic devices charges with voltage, and the described Section Point of described magnetic devices discharges with voltage.

14. equipment according to claim 12, wherein said input circuit through coupling receiving first voltage and second voltage, thereby produce duration of charging signal, first signal and secondary signal according to described first voltage and described second voltage.

15. equipment according to claim 14, wherein said control circuit through coupling receiving described duration of charging signal, described first signal and described secondary signal, thereby produce discharge time signal according to described duration of charging signal, described first signal and described secondary signal.

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