Bipolar transistor self-exciting Zeta converter
Technical field
The present invention relates to autonomous DC-DC converter, be applied to small power switch voltage stabilizing/stabilized current power supply, high-brightness LED drive circuit etc., especially a kind of auto-excitation type Zeta converter.
Background technology
Compare with small-power separated exciting DC-DC converter with the small-power linear power supply, small-power auto-excitation type DC-DC converter has that circuit structure is simple, the components and parts number is few, cost is low, self-starting and the self-shield performance is good, be suitable for wide, the efficient advantages of higher of operating voltage range.
Chinese patent ZL99108088.2 discloses a kind of auto-excitation type buck DC-DC converter, as shown in Figure 1.Form the major loop of Buck converter by PNP transistor Q1, coupling inductance L1, diode D1 and capacitor C 2, Vi, Vo are respectively direct current input, output voltage, and R7 is load.Coupling inductance L2 links to each other with base stage with the emitter of Q1 respectively with resistance R 3 by capacitor C 1, and the emitter and collector of PNP transistor Q2 also links to each other with base stage with the emitter of Q1 respectively.The base stage of Q1 is received the negative terminal of Vi by resistance R 4.R1 and R2 the be in series emitter that is connected to Q1 and the collector electrode two ends of NPN transistor Q3, the contact of R1 and R2 links to each other with the base stage of Q2.The series arm of R5 and R6 is connected to the Vo two ends, and the contact of R5 and R6 links to each other with the base stage of Q3.The emitter of Q3 is connected to the negative terminal of Vi.The operation principle of this auto-excitation type buck DC-DC converter is as follows: when circuit just powers on, and the Q1 saturation conduction, D1, Q2 all end, and Vi, Q1, L1, C2, R7, R5, R6 form the loop, and L1 and C2 are in charging energy storage state.In charging process, the electric current of L1 increases, and the output voltage of circuit increases, and correspondingly the collector volatge of penetrating of Q1 also increases thereupon, and the working point of Q1 is withdrawed from the saturation region gradually, and the voltage at L1 two ends descends simultaneously.Voltage by coupling L2 two ends also reduces thereupon, has strengthened the shunt volume to the Q1 base current simultaneously, causes the base current of Q1 and collector current to reduce, and further increases the collector volatge of penetrating of Q1, and circuit enters a kind of strong positive feedback.The result of this positive feedback work is that the collector current of Q1 reduces rapidly, and just to begin conducting be the L1 afterflow to D1 when less than the electric current of L1, and Q1 ends subsequently.At this moment, L1, C2, R7, R5, R6 and D1 form the loop, and L1 enters discharge and releases the energy state.Treat that the L1 discharge finishes, D1 ends, and Q1 is saturation conduction again, enters next from flyback cycle.Experience several all after dates, when output voltage reaches set point Vo, Voltage Feedback branch road R5, R6, Q3, R1, R2 and Q2 start working.When output voltage was higher than set point, the Q3 conducting caused the Q2 conducting and shunts the base current of a part of Q1, reaches the purpose that shortens the Q1 ON time, prolongs the Q1 turn-off time; When output voltage was lower than set point, Q3 ended, and caused Q2 to end, and recovered former state the switching time of Q1 again.Thus, circuit is realized the output voltage stabilizing.The weak point of this circuit is: essential coupling inductance L2 participates in the self-excitation work of circuit, and coupling inductance L1 and L2 make complicated, and the circuit elements device count is more, and is unfavorable to the cost and the volume that reduce product.
Chinese patent ZL00122441.7 discloses a kind of auto-excitation type boost DC-DC converter, as shown in Figure 2.Form the major loop of Boost converter by NPN transistor Q1, inductance L 1, diode D1 and capacitor C 1, Vi, Vo are respectively direct current input, output voltage, and R4 is load.The collector and emitter of NPN transistor Q2 links to each other with emitter with the base stage of Q1 respectively.The base stage of Q1 also links to each other with the anode of Vi by resistance R 1.The base stage of Q2 links to each other with R3 with R2.The other end of R2 links to each other with the collector electrode of Q1.The other end of R3 then is connected to the anode of Vo by voltage-stabiliser tube Z1.The operation principle of this auto-excitation type boost DC-DC converter is as follows: when circuit just powers on, and the Q1 saturation conduction, diode D1 ends, and Vi, L1, Q1 form the loop, and L1 is in charging energy storage state.In charging process, the electric current of inductance L 1 increases, and correspondingly the collection emitter voltage of Q1 also increases thereupon, and the working point of Q1 is withdrawed from the saturation region gradually.After Q1 collection emitter voltage was increased to certain value, the base current of Q2 and collector current began to increase.Simultaneously, owing to the shunting action of Q2 to the Q1 base current, the base current of Q1, collector current begin to reduce, and further increase the collection emitter voltage of Q1, and circuit enters a kind of strong positive feedback.The result of this positive feedback work is that the collector current of Q1 reduces rapidly, and D1 is the L1 afterflow with conducting when less than the electric current of L1, and Q1 ends subsequently.At this moment, Vi, L1, D1, C1 and R4 form the loop, and L1 enters discharge and releases the energy state, and the output voltage of circuit increases thereupon.Treat that the L1 discharge finishes, D1 ends, and Q1 is saturation conduction again, enters next from flyback cycle.Experience several all after dates, when output voltage reaches set point Vo, Voltage Feedback branch road Z1, R3, Q2 start working.When output voltage was higher than set point, the Z1 conducting had strengthened the shunting action of Q2 collector current to the Q1 base current, reached the purpose that shortens the Q1 ON time, prolongs the Q1 turn-off time; When output voltage was lower than set point, Z1 ended, and recovered former state the switching time of Q1 again.Thus, circuit is realized the output voltage stabilizing.The weak point of this circuit is: can only realize the boosting inverter of circuit, be of limited application.
Summary of the invention
For overcome existing auto-excitation type buck DC-DC converter circuit structure complexity, the components and parts number is more, and the narrower deficiency of auto-excitation type boost DC-DC converter range of application, the invention provides the bipolar transistor self-exciting Zeta converter that a kind of circuit structure is simple, the components and parts number is few, widen range of application.
The technical solution adopted for the present invention to solve the technical problems is:
A kind of bipolar transistor self-exciting Zeta converter, comprise PNP transistor Q1, inductance L 1, capacitor C 2, diode D1, inductance L 2 and capacitor C 3 are formed the major loop of Zeta converter, the voltage at load R6 two ends is VD Vo, the negative terminal of DC input voitage Vi links to each other with the negative terminal of VD Vo, described load R6 is in parallel with capacitor C 3, the contact of the anode of described VD Vo and capacitor C 3 links to each other with an end of inductance L 2, the other end of described inductance L 2 respectively with an end of capacitor C 2, the negative electrode of diode D1 links to each other, the anode of described diode D1 links to each other with the negative terminal of DC input voitage Vi, the other end of described capacitor C 2 links to each other with an end of inductance L 1, the other end of described inductance L 1 links to each other with the negative terminal of described VD Vi, the contact of the negative terminal of described VD Vo and capacitor C 3 links to each other with the negative terminal of DC input voitage Vi, described auto-excitation type Zeta converter also comprises PNP transistor Q2, the emitter of PNP transistor Q1 links to each other with the anode of DC input voitage Vi, the contact of inductance L 1 and capacitor C 2 links to each other with the collector electrode of PNP transistor Q1, the emitter of PNP transistor Q2 links to each other with the emitter of PNP transistor Q1, the collector electrode of PNP transistor Q2 links to each other with the base stage of PNP transistor Q1, the base stage of PNP transistor Q1 also is connected to the negative terminal of DC input voitage Vi by resistance R 1, the series arm of resistance R 2 and resistance R 3 is connected to the emitter and collector two ends of Q1, and the contact of resistance R 2 and resistance R 3 links to each other with the base stage of PNP transistor Q2.
As preferred a kind of scheme, described auto-excitation type Zeta converter also comprises Voltage Feedback branch road (as Fig. 3), the series arm of voltage-stabiliser tube Z1 and resistance R 5 is connected to VD Vo two ends, and the contact of voltage-stabiliser tube Z1 and resistance R 5 and the base stage of NPN transistor Q3 link to each other; The collector electrode of NPN transistor Q3 links to each other by the base stage of resistance R 4 and PNP transistor Q2, and the emitter of NPN transistor Q3 is connected to the negative terminal of DC input voitage Vi.
As preferred another kind of scheme, described auto-excitation type Zeta converter also comprises current feedback branch road (as Fig. 4): parallel branch one end that detects resistance R 5 and capacitor C 4 links to each other with the base stage of resistance R 6 with NPN transistor Q3, and the other end then links to each other with the negative terminal of DC input voitage Vi; The collector electrode of NPN transistor Q3 links to each other by the base stage of resistance R 4 and PNP transistor Q2, and the emitter of NPN transistor Q3 is connected to the negative terminal of DC input voitage Vi.
Further, described resistance R 3 two ends shunt capacitance C1 can accelerate the switching speed of Q2 and Q1.
Described auto-excitation type Zeta converter also comprises diode D2, the collector electrode of PNP transistor Q1 is connected with the anode of diode D2 with the contact of capacitor C 2, inductance L 1 is connected with the negative electrode of diode D2 with the contact of resistance R 3, can prevent that the electric current backflow of inductance L 1 is beneficial to circuit self-excitation work.
Technical conceive of the present invention is: two BJT self-excitation basic element circuits are applied in the Zeta converter, make them become new auto-excitation type DC-DC converter (shown in Fig. 3,4).Two BJT self-excitation basic element circuits are made up of transistor Q1 and Q2, resistance R 2 and R3.For thereby the switch working state that improves Q2 and Q1 improves the efficient of circuit, can be at R3 two ends shunt capacitance C1.Its feature is as follows: Q1 is the switching device in the Zeta converter major loop, and its emitter links to each other with the emitter and collector of Q2 respectively with base stage.Adopt resistance R 2 and R3 to form the collector volatge of penetrating that bleeder circuit detects Q1, gained detects the base stage that voltage inserts Q2.Penetrate collector volatge according to Q1, Q2 changes the shunt volume of its collector current to the Q1 base current, thereby realizes the turn-on and turn-off time of control Q1.What need to specify is, is applicable to that Q1 and the Q2 in two BJT self-excitation basic element circuits of Zeta converter is the PNP transistor.In addition, at BJT type auto-excitation type Zeta converter, for the refluence phenomenon appears in the startup that more helps circuit, the current i L1 that prevents input side inductance L 1 in the major loop, can be at the inductance L 1 series diode D2 of place.
For obtaining stable output voltage, between circuit output end and two BJT self-excitation basic element circuit, can increase by a Voltage Feedback branch road, can form (as Fig. 3) by NPN transistor Q3, voltage-stabiliser tube Z1, resistance R 4 and R5 etc.For obtaining stable output current, between circuit output end and two BJT self-excitation basic element circuit, can increase by a current feedback branch road so, can form (as Fig. 4) by NPN transistor Q3, resistance R 4, R5 and capacitor C 4 etc.
Beneficial effect of the present invention mainly shows: the BJT type auto-excitation type Zeta converter that the present invention proposes has the buck voltage transformation function of positive polarity, circuit structure is simple, the components and parts number is few, promptly do not need coupling inductance to participate in the self-excitation work of circuit, remedy the deficiency of voltage transformation function singleness again, be fit to very much application such as small power switch voltage stabilizing/stabilized current power supply, high-brightness LED drive circuit.
Description of drawings
Fig. 1 is the circuit diagram of existing auto-excitation type buck DC-DC converter.
Fig. 2 is the circuit diagram of existing auto-excitation type boost DC-DC converter.
Fig. 3 is the circuit diagram of the bipolar transistor self-exciting Zeta converter of embodiment 1.
Fig. 4 is the circuit diagram of the bipolar transistor self-exciting Zeta converter of embodiment 2.
Fig. 5 is the exemplary operation oscillogram of the bipolar transistor self-exciting Zeta converter of embodiment 1.
Fig. 6 is the exemplary operation oscillogram of the bipolar transistor self-exciting Zeta converter of embodiment 2.
Embodiment
Below in conjunction with accompanying drawing the present invention is further described.
Embodiment 1
With reference to Fig. 3 and Fig. 5, a kind of bipolar transistor self-exciting Zeta converter, comprise PNP transistor Q1, inductance L 1, capacitor C 2, diode D1, inductance L 2 and capacitor C 3 are formed the major loop of Zeta converter, the voltage at load R6 two ends is VD Vo, the negative terminal of DC input voitage Vi links to each other with the negative terminal of VD Vo, described load R6 is in parallel with capacitor C 3, the contact of the anode of described VD Vo and capacitor C 3 links to each other with an end of inductance L 2, the other end of described inductance L 2 respectively with an end of capacitor C 2, the negative electrode of diode D1 links to each other, the anode of described diode D1 links to each other with the negative terminal of DC input voitage Vi, the other end of described capacitor C 2 links to each other with an end of inductance L 1, the other end of described inductance L 1 links to each other with the negative terminal of described VD Vi, the contact of the negative terminal of described VD Vo and capacitor C 3 links to each other with the negative terminal of DC input voitage Vi, described auto-excitation type Zeta converter also comprises PNP transistor Q2, the emitter of PNP transistor Q1 links to each other with the anode of DC input voitage Vi, the contact of inductance L 1 and capacitor C 2 links to each other with the collector electrode of PNP transistor Q1, the emitter of PNP transistor Q2 links to each other with the emitter of PNP transistor Q1, the collector electrode of PNP transistor Q2 links to each other with the base stage of PNP transistor Q1, the base stage of PNP transistor Q1 also is connected to the negative terminal of DC input voitage Vi by resistance R 1, the series arm of resistance R 2 and resistance R 3 is connected to the emitter and collector two ends of Q1, and the contact of resistance R 2 and resistance R 3 links to each other with the base stage of PNP transistor Q2.
Described auto-excitation type Zeta converter also comprises diode D2, and the collector electrode of PNP transistor Q1 is connected with the anode of diode D2 with the contact of capacitor C 2, and inductance L 1 is connected with the negative electrode of diode D2 with the contact of resistance R 3.
The BJT type auto-excitation type Zeta converter using of output voltage stabilization shown in Figure 3 the Voltage Feedback branch road: the series arm of voltage-stabiliser tube Z1 and R5 is connected to the Vo two ends, and the contact of Z1 and R5 links to each other with the base stage of NPN transistor Q3; The collector electrode of Q3 links to each other by the base stage of resistance R 4 and Q2, and the emitter of Q3 is connected to the negative terminal of Vi.In addition,, can improve the switch working state of Q2 and Q1 at the R3 two ends of two BJT self-excitation basic element circuits shunt capacitance C1, helpful to the efficient that improves circuit.
Fig. 5 is the exemplary operation oscillogram of embodiment illustrated in fig. 31 BJT type auto-excitation type Zeta converter.Its circuit working principle is specific as follows:
(1) the circuit electrifying startup stage: t=0 when circuit just powers on, Q1 saturation conduction.Vi, Q1, D2 and L1 form the loop, and Vi, Q1, C2, L2, C3 and R6 then form another loop.This moment Q1 base current iQb1=(Vi-VQeb)/R1, Q1 to penetrate collector volatge vQec1 very little.Also do not reach the level that makes the Q2 conducting through R2 and the detected voltage of R3 dividing potential drop, Q2 is in cut-off state.D1 also is in cut-off state simultaneously.L1 and C2 are in charging energy storage state, but vC2<0.L2 and C3 also are in charging energy storage state.The current i L1 approximately linear that flows through L1 rises, and iL2 is also rising simultaneously.In the process of iL1 and iL2 rising, the iQc1 of Q1 and vQec1 are also increasing.When iQc1 rose and surpass HFE*iQb1, the saturation region was withdrawed from the working point of Q1, and vQec1 begins rapid rising.When R2 and the detected voltage of R3 dividing potential drop can make the Q2 conducting, the collector current of Q2 began to shunt a part of iQb1, and the reducing of iQb1 can further make vQec1 increase, and circuit enters a kind of strong positive feedback.The result of this pair of BJT self-excitation basic element circuit positive feedback work is that the collector current iQc1 of Q1 reduces rapidly, when iQc1 during less than inductive current iL1+iL2 sum D1 just to begin conducting be L1 and L2 afterflow, Q1 ends subsequently.T=t1 is L1, D1 and C2 formation loop constantly, and L2, C3, R6 and D1 form the loop.L1 and L2 enter discharge and release the energy state, and the output voltage of C2 both end voltage and circuit increases thereupon.T=t2 iL1 approximately linear constantly drops to zero, and Q1 is conducting once more, and D1 ends.Because the existence of D2 has been eliminated iL1 and has been become negative possibility.Circuit enters next from flyback cycle.Go through several cycles, after the output voltage of circuit reached set point Vo, circuit had just been finished the electrifying startup process, entered the steady operation stage.
(2) the circuit steady operation stage: after the output voltage of circuit reached set point Vo, the Voltage Feedback branch road of circuit just began to work.When output voltage is higher than set point, the Q3 conducting, the Q2 collector current reaches the purpose that shortens Q1 ON time (being t4-t3), prolongs Q1 deadline (being t5-t4) to the shunting action of Q1 base current in the two BJT self-excitation basic element circuits of increasing.When output voltage was lower than set point, Q3 ended, and two BJT self-excitation basic element circuits work alone, and recover former state the switching time of Q1 again.Thus, circuit can realize exporting voltage stabilizing.
Embodiment 2
With reference to Fig. 4 and Fig. 6, present embodiment also comprises the current feedback branch road: parallel branch one end that detects resistance R 5 and capacitor C 4 links to each other with the base stage of NPN transistor Q3 with R6, and the other end then links to each other with the negative terminal of Vi; The collector electrode of Q3 links to each other by the base stage of resistance R 4 and Q2, and the emitter of Q3 is connected to the negative terminal of Vi.
The course of work of present embodiment is:
(1) the circuit electrifying startup stage identical with embodiment 1, go through several cycles, after the output current of circuit reached set point Io, circuit had just been finished the electrifying startup process, entered the steady operation stage.
(2) the circuit steady operation stage: after the output current of circuit reached set point Io, the current feedback branch road of circuit just began to work.When output current is higher than set point, the Q3 conducting, the Q2 collector current reaches the purpose that shortens Q1 ON time (being t4-t3), prolongs Q1 deadline (being t5-t4) to the shunting action of Q1 base current in the two BJT self-excitation basic element circuits of increasing.When output current was lower than set point, Q3 ended, and two BJT self-excitation basic element circuits work alone, and recover former state the switching time of Q1 again.Thus, circuit can realize exporting current stabilization.
Other structures of present embodiment are identical with embodiment 1 with the course of work.