CN101350553A - Power switching circuit with load open circuit protection - Google Patents

Abstract

The present invention discloses a power supply switching circuit with loads open-circuit protection, which is electrically connected with the power supply of a first voltage and transmits outwards a second voltage to drive the load. The power supply switching circuit comprises a DC-to-DC converter and a rectification component; the DC-to-DC converter is used for receiving the power supply, transforming the first voltage into the second voltage, and transmitting outwards the second voltage to the load; the rectification component is arranged between the output end and the input end of the DC-to-DC converter and forms a discharging loop with the DC-to-DC converter; the discharging loop is used for releasing the surge voltage of the DC-to-DC converter when the load has an open circuit. Because of the direct arrangement of the rectification component (such as a diode) between the input end and the output end, when the load has an open-circuit failure, the power supply switching circuit can provide a releasing path of surge voltage. Because of no use of Zener diode for protection, the manufacturing cost is not greatly influenced. Moreover, the control circuit requires no detection, so the structure is simple.

Description

Power-switching circuit with load open circuit protection

Technical field

The present invention relates to a kind of power-switching circuit, relate in particular to a kind of power-switching circuit with load open circuit protection.

Background technology

(Light Emitting Diode LED) has that volume is little, luminous efficiency is high, the life-span is long, reliability is strong, low power consuming, no mercury pollution and not fragile an etc. advantage, has widelyd popularize at present and has been used for replacing traditional lighting gradually because light-emitting diode.

Please refer to Fig. 1, be the drive circuit schematic diagram of present light-emitting diode.As shown in Figure 1, first end of switch SW is electrically connected to first end of diode D, and second end of switch SW is electrically connected to first end of power supply Vi, and second end of power supply Vi is electrically connected to earth terminal; First end of input capacitance Ci and second end of switch SW electrically connect, and second end of input capacitance Ci is electrically connected to earth terminal; First end of diode D (being negative terminal or N end) electrically connects with first end of switch SW, and second end of diode D (being anode or P end) is electrically connected to earth terminal; First end of inductance L and first end of diode D electrically connect, and second end of inductance L is electrically connected to first end of output capacitance Co, and second end of output capacitance Co is electrically connected to earth terminal; LED first end (be negative terminal or N end) be electrically connected to earth terminal, LED second end (be anode or P end) be electrically connected to first end of output capacitance Co, and the type of drive of Fig. 1 has following problem: (1) drive circuit need reduce the output voltage ripple of light-emitting diode by output capacitance Co, but the output capacitance Co that adds not only takies the overall space of drive circuit its manufacturing cost is risen.(2) when power supply Vi does not close (being the live wire operation) moment replacing light-emitting diode (LED) module, can cause light-emitting diode (LED) module to damage, when particularly being replaced with light-emitting diode (LED) module with less light-emitting diode quantity, for example, originally be the module of 10 light-emitting diodes, have 40V (to suppose the forward conducting voltage V of each light-emitting diode approximately on the output voltage V o this moment _FBe 4V), when being replaced with the module of 2 light-emitting diodes since output capacitance Co remaining voltage, can cause the big electric current of moment to flow through light-emitting diode, and then cause light-emitting diode to burn.(3) so because there is the output capacitance Co can't fast start circuit, otherwise burst current can be very big, so need to do slow start-up control design.

Please refer to Fig. 2, be another drive circuit schematic diagram of present light-emitting diode.As shown in Figure 2, first end of switch SW is electrically connected to first end of diode D, and second end of switch SW is electrically connected to first end of power supply Vi, and second end of power supply Vi is electrically connected to earth terminal; First end of input capacitance Ci and second end of switch SW electrically connect, and second end of input capacitance Ci is electrically connected to earth terminal; First end of diode D (being negative terminal or N end) electrically connects with first end of switch SW, and second end of diode D (being anode or P end) is electrically connected to earth terminal; First end of inductance L and first end of diode D electrically connect, second end of inductance L electrically connect LED second end (being anode or P end), LED first end (being negative terminal or N end) be electrically connected to second end (being anode or P end) of diode D.The drive circuit of Fig. 2 is by strengthening inductance L to reduce the output voltage ripple of light-emitting diode, therefore the output voltage ripple that must output capacitance Co reduce light-emitting diode, so can reduce the overall volume and the manufacturing cost of drive circuit, and OCL output capacitance-less Co, circuit also capable of fast starting, but when the failure situations of open circuit takes place in light-emitting diode, being stored in energy on the inductance L can't discharge and produce surge voltage more than hundreds of volts, cause danger, particularly heal when big when inductance L, the surge voltage that produces also can heal seriously.

For example: suppose that average current on the light-emitting diode is that parasitic capacitance on 500mA, inductance L=220uH, the circuit is 1000pF.According to the conservation of energy: $\frac{1}{2}L\·{\mathrm{\ΔI}}^2=\frac{1}{2}C\·{\mathrm{\ΔV}}^2,$ When the light-emitting diode open-circuit fault, can produce $\mathrm{\ΔV}=\mathrm{\ΔI}\·\sqrt{\frac{L}{C}}=0.5\·\sqrt{\frac{220u}{1000p}}=234.52V$ Surge voltage.This is breakneck, and especially under inductance L electric current bigger, light-emitting diode was healed high situation, the surge voltage that open fault produced can be more serious.

Please refer to Fig. 3, be another drive circuit schematic diagram of present light-emitting diode.As shown in Figure 3, first end of switch SW is electrically connected to first end of diode D, and second end of switch SW is electrically connected to first end of power supply Vi, and second end of power supply Vi is electrically connected to earth terminal; First end of input capacitance Ci and second end of switch SW electrically connect, and second end of input capacitance Ci is electrically connected to earth terminal; First end of diode D (being negative terminal or N end) electrically connects with first end of switch SW, and second end of diode D (being anode or P end) is electrically connected to earth terminal; First end of inductance L and first end of diode D electrically connect, and second end of inductance L is electrically connected to first end of Zener diode Dz (being negative terminal or N end), and second end of Zener diode Dz (being anode or P end) is electrically connected to earth terminal; LED first end (be negative terminal or N end) be electrically connected to earth terminal, LED second end (being anode or P end) be electrically connected to Zener diode Dz first end (being negative terminal or N end).The drive circuit of Fig. 3 has added Zener diode Dz and has protected; when light-emitting diode generation open fault; the energy that is stored in inductance L can discharge via Zener diode Dz; therefore the surge voltage that inductance L produced can be by Zener diode Dz strangulation at its breakdown voltage, to reach the effect of protection.

But the breakdown voltage that adopts the Zener diode Dz of this kind protected mode need be higher than the number of the light-emitting diode of series connection at least multiply by forward conducting voltage V _FValue.For example, 15 light-emitting diodes of drive circuit output series connection are supposed the forward conducting voltage V of each light-emitting diode _FBe 4V; then the breakdown voltage of Zener diode Dz must be higher than more than the 60V at least; with regard to the Zener diode Dz that selects high wattage, high breakdown voltage on being applied in the high power illumination occasion for use as with regard to the protection; for reality on the cost is costliness and white elephant, and uses and go up and need multiply by its forward conducting voltage V according to the number of different light-emitting diodes _FValue, the foundation of choosing with as Zener diode Dz also lacks flexibility in design.

Please refer to Fig. 4, be another drive circuit schematic diagram of present light-emitting diode.As shown in Figure 4, first end of switch SW is electrically connected to first end of diode D, and second end of switch SW is electrically connected to first end of power supply Vi, and second end of power supply Vi is electrically connected to earth terminal; First end of input capacitance Ci and second end of switch SW electrically connect, and second end of input capacitance Ci is electrically connected to earth terminal; First end of diode D (being negative terminal or N end) electrically connects with first end of switch SW, and second end of diode D (being anode or P end) is electrically connected to earth terminal; First end of inductance L and first end of diode D electrically connect, second end of inductance L is electrically connected to first end of resistance R 1, and second end of resistance R 1 is electrically connected to first end of resistance R 2 and the non-inverting input of comparator, second end of resistance R 2 is electrically connected to earth terminal, and the inverting input of comparator receives reference voltage V _RefThe output of comparator is electrically connected to the input of gate drivers, the output of gate drivers is electrically connected to the grid of transistor switch NMOS, the source electrode of transistor switch NMOS is electrically connected to first end of resistance R 3, second end of resistance R 3 is electrically connected to earth terminal, and the drain electrode of transistor switch NMOS is electrically connected to second end of inductance L; LED first end (be negative terminal or N end) be electrically connected to earth terminal, LED second end (being anode or P end) be electrically connected to second end of inductance L.Fig. 4 is by detecting the voltage Vo of drive circuit output, with the back of its dividing potential drop and reference voltage V _RefCompare, if detect the voltage dividing potential drop afterwards greater than reference voltage V _Ref, promptly judge light-emitting diode generation open fault situation.At this moment, the gate drivers output drive signal is with transistor switch NMOS conducting, and the energy on the inductance L just can be discharged into zero via transistor switch NMOS and resistance R 3, the destruction of avoiding producing surge voltage.Owing to must not utilize Zener diode Dz, therefore can not cause the burden on the price, but it is comparatively complicated to detect control circuit, and input and control has delay issue as protection circuit.

Summary of the invention

Technical problem to be solved by this invention is to provide a kind of power-switching circuit of tool load open circuit protection; discharge the surge voltage that direct current is produced when the load open circuit direct current transducer by discharge loop; when avoiding plugging load, cause the problem of surge voltage.

The power-switching circuit of disclosed tool load open circuit protection according to the present invention, be electrically connected to the power supply of first voltage, and export second voltage (for example to drive its load, light-emitting component), and power-switching circuit includes: direct current is to direct current transducer, receive this power supply, and be second voltage, to export second voltage to light-emitting diode with first voltage transitions; And rectifier cell, be arranged between the output and input of direct current, and direct current transducer constituted a discharge loop, and discharge loop is in order to discharge the surge voltage that direct current is produced when the light-emitting diode open-circuit direct current transducer with direct current to direct current transducer.

In addition, the power-switching circuit that the present invention discloses, receiving the DC power supply of first voltage and changing first voltage is second voltage, to export second voltage to one load, includes: switch has first end and second end, alternative conducting or cut out; Input capacitance has first end and second end, and second end of first end of input capacitance and switch electrically connects, and second end of input capacitance is electrically connected to an earth terminal; Diode has first end and second end, and first end of first end of diode and switch electrically connects, and second end of diode is electrically connected to earth terminal; Inductance has first end and second end, and first end of inductance and first end of diode electrically connect, and carry out energy storage by power supply; And rectifier cell, have first end and second end, and first end of rectifier cell being electrically connected to first end of input capacitance, second end of rectifier cell is electrically connected to second end of this inductance; Wherein when load was open circuit, inductance, input capacitance, diode and rectifier cell constituted discharge loop to discharge a surge voltage, so that the energy loopback of surge voltage is stored in the input capacitance.Power-switching circuit by this tool load open circuit protection; directly between the input of power-switching circuit and output, a rectifier cell is set (for example; diode); with when the load open circuit fault; the surge voltage release way is provided; since need not utilize Zener diode protection, can not cause too big burden to manufacturing cost, and need not detect control circuit so circuit framework is simple.

The power-switching circuit of tool load open circuit protection of the present invention; directly between the input of power-switching circuit and output, a rectifier cell is set (for example; diode); with when the load open circuit fault; the surge voltage release way is provided; since need not utilize Zener diode protection, can not cause too big burden to manufacturing cost, and need not detect control circuit so circuit framework is simple.

Relevant characteristics and implementation of the present invention, conjunction with figs. is described in detail as follows as most preferred embodiment now.

Description of drawings

Fig. 1 is the drive circuit schematic diagram of the light-emitting diode of prior art;

Fig. 2 is another drive circuit schematic diagram of the light-emitting diode of prior art;

Fig. 3 is another drive circuit schematic diagram of the light-emitting diode of prior art;

Fig. 4 is another drive circuit schematic diagram of the light-emitting diode of prior art;

Fig. 5 is a system block diagrams of the present invention;

Fig. 6 is the circuit diagram of first embodiment of the invention; And

Fig. 7 A and Fig. 7 B are the circuit diagram of second embodiment of the invention.

Wherein, Reference numeral:

10: power supply 20: direct current is to direct current transducer

30: rectifier cell 40: load

Ci: input capacitance Co: output capacitance

D: diode D1: first diode

D2: the second diode Dz: Zener diode

LED: light-emitting diode L: inductance

NMOS: transistor switch R1: resistance

R2: resistance R 3: resistance

SWT: switch SW: first switch

SW: second switch Vi: power supply

Vo: output voltage V _Ref: reference voltage

Embodiment

Please refer to Fig. 5, be system block diagrams of the present invention.As shown in Figure 5, the power-switching circuit of tool load open circuit protection of the present invention includes: direct current is to direct current transducer 20 and rectifier cell 30.

Power supply 10 has the DC power supply of first voltage, electrically connects with the input of direct current to direct current transducer 20.

Direct current is to direct current transducer 20, electrically connects with power supply 10, and in order to receiving first voltage of power supply 10 outputs, and first voltage of conversion electric power 10 is second voltage, and second voltage can be greater than or less than first voltage.Wherein direct current can be a buck (buck) direct current to direct current transducer to direct current transducer 20.

Rectifier cell 30, be arranged between the input and output of direct current to direct current transducer 20, and direct current transducer 20 is constituted a discharge loop with direct current, and discharge loop is in order to discharge the surge voltage that direct current is produced when load 40 open circuits direct current transducer 20.

Load 40, electrically connect with the output of direct current direct current transducer 20, to receive second voltage of direct current transducer 20 outputs, wherein the load in the embodiment of the invention 40 be light-emitting component (for example, a plurality of light-emitting diodes that are connected in series), and receive second voltage of direct current to direct current transducer 20 outputs, to produce the brightness of corresponding second voltage.

Please refer to Fig. 6, be the circuit diagram of first embodiment of the invention.As shown in Figure 6, the power-switching circuit of tool load open circuit protection of the present invention includes switch SW T, input capacitance Ci, the first diode D1, inductance L, the second diode D2.

Switch SW T has first end and second end, and first end of switch SW T is electrically connected to first end of the first diode D1, and second end of switch SW T is electrically connected to first end of power supply Vi, and second end of power supply Vi is electrically connected to earth terminal.

Input capacitance Ci has first end and second end, and first end of input capacitance Ci and second end of switch SW T electrically connect, and second end of input capacitance Ci is electrically connected to earth terminal.

The first diode D1 has first end (being negative terminal or N end) and second end (being anode or P end), and first end of the first diode D1 and first end of switch SW T electrically connect, and second end of the first diode D1 is electrically connected to earth terminal.

Inductance L has first end and second end, and first end of first end of inductance L and the first diode D1 electrically connects, and second end of inductance L is electrically connected to second end of the second diode D2.

The second diode D2, have first end (being negative terminal or N end) and second end (being anode or P end), first end of the second diode D2 is electrically connected to first end of input capacitance Ci, second end of the second diode D2 is electrically connected to second end of inductance L, wherein when LED is open circuit, inductance L, the second diode D2, input capacitance Ci and the first diode D1 constitute a discharge loop to discharge a surge voltage, so that the energy loopback of surge voltage is stored among the input capacitance Ci.The circuit operation principle below is described.

When switch SW T conducting (ON), power supply Vi provides second voltage to LED via inductance L, and makes inductance L carry out energy storage, and when switch SW T closed (OFF), inductance L provided second voltage to LED.

Because inductance L can be considered current source, when LED generation open fault, though there is not the energy on the output capacitance Co absorption inductor L, but the still necessary afterflow of inductance L electric current, this moment, the second diode D2 just was equivalent to provide one the path that releases energy, and the energy on the inductance L is transmitted back to input capacitance Ci via the second diode D2, so, can make the electric current on the inductance L slowly drop to zero, avoid moment to produce high surge voltage.Simultaneously, be transmitted back to the energy of input capacitance Ci, also can be used as the energy that utilizes again.

In addition, direct current shown in Figure 6 is an asynchronous rectified type buck power-switching circuit to the framework of direct current transducer, but is not expression in order to limit the present invention, and the present invention also can use the buck power-switching circuit at synchronous commutation type, shown in Fig. 7 A and Fig. 7 B.In addition, load 40 also is not limited to the light-emitting diode of light-emitting component, can for example be internal memory, processor, controller or stepper motor or the like.

Please refer to Fig. 7 A and Fig. 7 B, be the circuit diagram of second embodiment of the invention.Shown in Fig. 7 A and Fig. 7 B, the power-switching circuit of tool load open circuit protection of the present invention includes first switch SW, input capacitance Ci, second switch SW, inductance L, the second diode D2.

First switch SW has first end and second end, and first end of first switch SW is electrically connected to first end of second switch SW, and second end of first switch SW is electrically connected to first end of power supply Vi, and second end of power supply Vi is electrically connected to earth terminal.

Input capacitance Ci has first end and second end, and first end of input capacitance Ci and second end of first switch SW electrically connect, and second end of input capacitance Ci is electrically connected to earth terminal.

Second switch SW, have first end and second end, first end of second switch SW and first end of first switch SW electrically connect, second end of second switch SW is electrically connected to earth terminal, wherein the action of second switch SW is opposite with first switch SW, and promptly when second switch SW was conducting (ON), then first switch SW was for closing (OFF), when second switch SW when closing (OFF), then first switch SW is conducting (ON).

Inductance L has first end and second end, and first end of inductance L and first end of second switch SW electrically connect, and second end of inductance L is electrically connected to second end of the second diode D2.

The second diode D2 has first end (being negative terminal or N end) and second end (being anode or P end), and first end of the second diode D2 is electrically connected to first end of input capacitance Ci, and second end of the second diode D2 is electrically connected to second end of inductance L.Below the explanation second embodiment in when load generation open fault, the circuit operation principle of discharge loop.

Shown in Fig. 7 A, when the first switch SW conducting (ON), then second switch SW closes (OFF), and power supply Vi provides second voltage to LED via inductance L, and makes inductance L carry out energy storage.

When LED generation open fault, though there is not energy on the output capacitance Co absorption inductor L, the inductance L electric current still must afterflow, and this moment, the second diode D2, first switch SW and inductance L formed a discharge loop.

Shown in Fig. 7 B, when first switch SW is closed (OFF), then second switch SW conducting (ON), inductance L provides second voltage to LED.

Because inductance L can be considered current source, when LED generation open fault, though there is not the energy on the output capacitance Co absorption inductor L, but the still necessary afterflow of inductance L electric current, inductance L, the second diode D2, input capacitance Ci and second switch SW constitute a discharge loop to discharge surge voltage at this moment, and the energy on the inductance L is transmitted back to input capacitance Ci via the second diode D2.So, can make the electric current on the inductance L slowly drop to zero, avoid moment to produce high surge voltage.Simultaneously, be transmitted back to the energy of input capacitance Ci, also can be used as the energy that utilizes again.

The switch SW T of above-mentioned Fig. 6 can be electronic switch (for example, transistor), and first switch SW among Fig. 7 A and Fig. 7 B and second switch SW all can be electronic switch (for example, transistor).

In sum; the power-switching circuit of tool load open circuit protection of the present invention; directly between the input of power-switching circuit and output, a rectifier cell is set (for example; diode); with when the load open circuit fault, provide the surge voltage release way, owing to need not utilize Zener diode protection; so can not cause too big burden, and need not detect control circuit so circuit framework is simple to manufacturing cost.

Certainly; the present invention also can have other various embodiments; under the situation that does not deviate from spirit of the present invention and essence thereof; being familiar with those of ordinary skill in the art ought can make various corresponding changes and distortion according to the present invention, but these corresponding changes and distortion all should belong to the protection range of the appended claim of the present invention.

Claims (12)

1, a kind of power-switching circuit of tool load open circuit protection is electrically connected to the power supply of one first voltage, and exports one second voltage to drive its load, it is characterized in that this power-switching circuit includes:

One direct current receives this power supply to direct current transducer, and is this second voltage with this first voltage transitions, to export this second voltage to this load; And

One rectifier cell is arranged between the output and input of this direct current to direct current transducer, and with this direct current direct current transducer is constituted a discharge loop, and this discharge loop is in order to discharge the surge voltage that this direct current is produced when this load open circuit direct current transducer.

2, power-switching circuit according to claim 1 is characterized in that, this load is a light-emitting component.

3, power-switching circuit according to claim 1 is characterized in that, this light-emitting component is at least one light-emitting diode.

4, power-switching circuit according to claim 1 is characterized in that, this rectifier cell is a diode.

5, power-switching circuit according to claim 1 is characterized in that, this direct current is that a buck direct current is to direct current transducer to direct current transducer.

6, power-switching circuit according to claim 1 is characterized in that, this direct current includes direct current transducer:

One switch has one first end and one second end;

One input capacitance has one first end and one second end, and this second end of this of this input capacitance first end and this switch electrically connects, and this of this input capacitance second end is electrically connected to an earth terminal;

One diode has one first end and one second end, and this first end of this of this diode first end and this switch electrically connects, and this of this diode second end is electrically connected to this earth terminal; And

One inductance has one first end and one second end, and this first end of this of this inductance first end and this diode electrically connects;

When this load was open circuit, this inductance, this rectifier cell, this input capacitance, this diode constituted this discharge loop.

7, power-switching circuit according to claim 6 is characterized in that, this switch is a transistor.

8, power-switching circuit according to claim 1 is characterized in that, this direct current includes direct current transducer:

One first switch has one first end and one second end;

One input capacitance has one first end and one second end, and this second end of this of this input capacitance first end and this first switch electrically connects, and this of this input capacitance second end is electrically connected to an earth terminal;

One second switch has one first end and one second end, and this first end of this of this second switch first end and this first switch electrically connects, and this of this second switch second end is electrically connected to this earth terminal; And

One inductance has one first end and one second end, and this first end of this of this inductance first end and this second switch electrically connects;

When this first switch was conducting, this second switch was for closing; When this second switch was conducting, this first switch was for cutting out.

9, power-switching circuit according to claim 8 is characterized in that, when this load was open circuit, this inductance, this rectifier cell, this input capacitance, this second switch constituted this discharge loop.

10, power-switching circuit according to claim 8 is characterized in that, when this load was open circuit, this inductance, this rectifier cell and this first switch constituted this discharge loop.

11, power-switching circuit according to claim 8 is characterized in that, this first switch is a transistor.

12, power-switching circuit according to claim 8 is characterized in that, this second switch is a transistor.

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