CN102510217A

CN102510217A - MOSFET-based auto-excitation type Zeta converter

Info

Publication number: CN102510217A
Application number: CN201110374592XA
Authority: CN
Inventors: 陈怡�; 南余荣
Original assignee: Zhejiang University of Technology ZJUT
Current assignee: Jinhu Agricultural And Sideline Products Marketing Association
Priority date: 2011-11-22
Filing date: 2011-11-22
Publication date: 2012-06-20
Anticipated expiration: 2031-11-22
Also published as: CN102510217B

Abstract

An MOSFET (Metal-Oxide -Semiconductor Field Effect Transistor)-based auto-excitation type Zeta converter comprises a Zeta converter main loop consisting of an input capacitor Ci, an N-type MOSFET M1, an inductor L1, a capacitor C, a diode D, an inductor L2 and a capacitor Co. The converter further comprises an auxiliary power supply U1, and adopts a single-MOSFET basic auto-excitation unit circuit consisting of the N-type MOSFET M1, a diode D1, a diode D2, a resistor R1, a resistor R2, a resistor R3, a capacitor C1, a hysteresis comparator U3 and a drive circuit U2. The MOSFET-based auto-excitation type Zeta converter provided by the invention has the advantages of higher efficiency and wider applicable power range.

Description

Auto-excitation type Zeta converter based on MOSFET

Technical field

The present invention relates to autonomous DC-DC (DC-DC) converter, be applied to switch voltage-stabilizing or stabilized current power supply, high-brightness LED drive circuit etc., especially a kind of auto-excitation type Zeta converter.

Background technology

Compare with separated exciting DC-DC converter with linear (voltage stabilizing or current stabilization) adjuster, auto-excitation type DC-DC converter has the high remarkable advantage of cost performance.What Fig. 1 provided is a kind of auto-excitation type Zeta converter based on BJT (bipolar transistor); Comprise the Zeta converter major loop of forming by input capacitance Ci, positive-negative-positive BJT Q1, diode D1, inductance L 1, capacitor C, diode D, inductance L 2 and output capacitance Co; Input capacitance Ci is parallelly connected with direct voltage source Vi; Output capacitance Co voltage is VD Vo, and load Ro is parallelly connected with output capacitance Co, and the negative terminal of direct voltage source Vi links to each other with the negative terminal of VD Vo and the anode of diode D; The anode of direct voltage source Vi links to each other with the emitter of positive-negative-positive BJT Q1; The collector electrode of positive-negative-positive BJT Q1 links to each other with an end of the anode of diode D1 and capacitor C, and the negative electrode of diode D1 links to each other with an end of inductance L 1, and the other end of inductance L 1 links to each other with the negative terminal of direct voltage source Vi; The other end of capacitor C links to each other with an end of inductance L 2 and the negative electrode of diode D, and the other end of inductance L 2 links to each other with the anode of output voltage V o.Auto-excitation type Zeta converter based on BJT shown in Figure 1 also comprises positive-negative-positive BJT Q2; The emitter and collector of positive-negative-positive BJT Q2 links to each other with base stage with the emitter of positive-negative-positive BJT Q1 respectively; The base stage of positive-negative-positive BJT Q1 also is connected to the negative terminal of direct voltage source Vi through resistance R 1; Resistance R 3 is formed parallel branch with capacitor C 1; One end of said parallel branch links to each other with the negative electrode of diode D1, and the other end of said parallel branch links to each other with the base stage of positive-negative-positive BJT Q2 and an end of resistance R 2, and the other end of resistance R 2 links to each other with the emitter of positive-negative-positive BJT Q2.Auto-excitation type Zeta converter based on BJT shown in Figure 1 also comprises the Voltage Feedback branch road; The negative electrode of voltage-stabiliser tube Z1 links to each other with the anode of VD Vo; The anode of voltage-stabiliser tube Z1 links to each other with an end of resistance R 5 and the base stage of NPN type BJT Q3; The collector electrode of NPN type BJT Q3 links to each other with the base stage of positive-negative-positive BJT Q2 through resistance R 4, and the emitter of NPN type BJT Q3 and the other end of resistance R 5 are connected to the negative terminal of direct voltage source Vi.The weak point of this circuit is: main switch Q1 adopts BJT, because of the operating characteristic of BJT causes circuit efficiency not high enough, relatively is fit to the occasion of small-power (several watts levels below).

Summary of the invention

Not high enough and only be applicable to that low power deficiency, the present invention provide that a kind of efficient is higher, the auto-excitation type Zeta converter based on MOSFET (mos field effect transistor) of suitable power wider range for overcoming based on the auto-excitation type Zeta transducer effciency of BJT.

The technical solution adopted for the present invention to solve the technical problems is:

A kind of auto-excitation type Zeta converter based on MOSFET; Comprise the Zeta converter major loop of forming by input capacitance Ci, N type MOSFET M1, inductance L 1, capacitor C, diode D, inductance L 2 and capacitor C o; Input capacitance Ci is parallelly connected with direct voltage source Vi; Output capacitance Co voltage is VD Vo, and load Ro is parallelly connected with output capacitance Co, and the anode of direct voltage source Vi links to each other with the drain electrode of N type MOSFET M1; The source electrode of N type MOSFETM1 links to each other with an end of an end of inductance L 1 and capacitor C; The other end of inductance L 1 links to each other with an end of resistance R 5, and the other end of resistance R 5 links to each other with the negative terminal of direct voltage source Vi, and the other end of capacitor C links to each other with the negative electrode of diode D and an end of inductance L 2; The other end of inductance L 2 links to each other with the anode of output voltage V o, and the negative terminal of direct voltage source Vi links to each other with the negative terminal of output voltage V o and the anode of diode D; Said auto-excitation type Zeta converter based on MOSFET also comprises accessory power supply U1, drive circuit U2 and hysteresis comparator U3; Accessory power supply U1 is used to provide drive circuit U2 and the required DC power supply voltage of hysteresis comparator U3 work, and DC input voitage Vi is boosted or the conversion process of step-down; The input of drive circuit U2 is connected with the output of hysteresis comparator U3, and the output of drive circuit U2 links to each other with the gate pole of N type MOSFET M1, and drive circuit U2 is that turning on and off of N type MOSFETM1 provides driving; The input of hysteresis comparator U3 links to each other with an end of capacitor C 1, resistance R 1, resistance R 2 and resistance R 3; The other end of capacitor C 1 and resistance R 3 links to each other with the negative terminal of direct voltage source Vi; The other end of resistance R 1 links to each other with the negative electrode of diode D1; The other end of resistance R 2 links to each other with the anode of diode D2, and the negative electrode of the anode of diode D1 and diode D2 links to each other with the source electrode of N type MOSFET M1.

Said auto-excitation type Zeta converter based on MOSFET also comprises the overcurrent protection branch road; Said overcurrent protection branch road comprises resistance R 6, capacitor C 2, NPN type BJT Q2 and positive-negative-positive BJT Q1; One end of resistance R 6 links to each other with the contact of inductance L 1 with resistance R 5; The other end of resistance R 6 links to each other with an end of capacitor C 2 and the base stage of NPN type BJT Q2; The other end of capacitor C 2 links to each other with the emitter of NPN type BJT Q2 and the negative terminal of direct voltage source Vi; The collector electrode of NPN type BJT Q2 links to each other with the base stage of positive-negative-positive BJT Q1, and the emitter of positive-negative-positive BJT Q1 links to each other with the source electrode of N type MOSFET M1, and the collector electrode of positive-negative-positive BJT Q1 links to each other with the input of hysteresis comparator U3.

As preferred a kind of scheme: said auto-excitation type Zeta converter based on MOSFET also comprises the Voltage Feedback branch road; Said Voltage Feedback branch road comprises resistance R 7, capacitor C 3, resistance R 8, NPN type BJT Q3, resistance R 4 and positive-negative-positive BJT Q1; Resistance R 7 is formed parallel branch with capacitor C 3; One end of said parallel branch links to each other with the anode of VD Vo; The other end of said parallel branch links to each other with an end of resistance R 8 and the base stage of NPN type BJT Q3, and the emitter of NPN type BJT Q3 links to each other with the other end of resistance R 8 and the negative terminal of direct voltage source Vi, and the collector electrode of NPN type BJT Q3 links to each other with the base stage of positive-negative-positive BJT Q1 through resistance R 4.

Among the present invention, overcurrent protection branch road and Voltage Feedback branch road can shared positive-negative-positive BJTQ1.

As preferred another kind of scheme: said auto-excitation type Zeta converter based on MOSFET also comprises the current feedback branch road; Said current feedback branch road comprises detection resistance R 9, voltage amplifier U4, resistance R 7, capacitor C 3, resistance R 8, NPN type BJT Q3, resistance R 4 and positive-negative-positive BJT Q1; Detect resistance R 9 and form series arm with load Ro; Said series arm is parallelly connected with output capacitance Co; An end that detects resistance R 9 links to each other with the negative terminal of direct voltage source Vi, and the other end that detects resistance R 9 links to each other with the end of load Ro and the input of voltage amplifier U4, and resistance R 7 is formed parallel branch with capacitor C 3; One end of said parallel branch links to each other with the output of voltage amplifier U4; The other end of said parallel branch links to each other with an end of resistance R 8 and the base stage of NPN type BJT Q3, and the emitter of NPN type BJT Q3 links to each other with the other end of resistance R 8 and the negative terminal of direct voltage source Vi, and the collector electrode of NPN type BJT Q3 links to each other with the base stage of positive-negative-positive BJT Q1 through resistance R 4.

Among the present invention, overcurrent protection branch road and current feedback branch road can shared positive-negative-positive BJTQ1.

Technical conceive of the present invention is: the basic self-excitation element circuit of single MOSFET is applied in the Zeta converter, makes it to become new auto-excitation type DC-DC converter (like Fig. 2, shown in 3).The basic self-excitation element circuit of single MOSFET is made up of N type MOSFET M1, diode D1, diode D2, resistance R 1, resistance R 2, resistance R 3, capacitor C 1, hysteresis comparator U3 and drive circuit U2.Its characteristic is following: M1 is the switching device in the Zeta converter major loop; The gate pole of M1 links to each other with the output of drive circuit U2; The source electrode of M1 links to each other with the anode of diode D1 and the negative electrode of diode D2; The negative electrode of D1 links to each other with an end of resistance R 1, and the anode of D2 links to each other with an end of resistance R 2, and the other end of resistance R 1 and resistance R 2 all links to each other with the input of hysteresis comparator U3, an end of capacitor C 1 and an end of resistance R 3; The other end of capacitor C 1 and resistance R 3 is connected to the negative terminal of direct voltage source Vi, and the output of hysteresis comparator U3 links to each other with the input of drive circuit U2.

For obtaining stable VD; Between the port of the output of Zeta converter major loop and the basic self-excitation element circuit of single MOSFET, can increase a Voltage Feedback branch road, can form (like Fig. 2) by positive-negative-positive BJT Q1, NPN type BJT Q3, resistance R 4, resistance R 7, resistance R 8 and capacitor C 3 etc.For obtaining stable average anode current; Between the port of the output of Zeta converter major loop and the basic self-excitation element circuit of single MOSFET, can increase a current feedback branch road, can form (like Fig. 3) by positive-negative-positive BJT Q1, NPN type BJT Q3, resistance R 4, resistance R 7, resistance R 8, resistance R 9, capacitor C 3 and voltage amplifier U4 etc.For preventing the L1 overcurrent; Between the port of the output of Zeta converter major loop and the basic self-excitation element circuit of single MOSFET, can increase an overcurrent protection branch road, can form (like Fig. 2 and Fig. 3) by resistance R 5, resistance R 6, capacitor C 2, NPN type BJT Q2, positive-negative-positive BJT Q1 etc.

Beneficial effect of the present invention mainly shows: the present invention proposes to have based on the auto-excitation type Zeta converter of MOSFET the voltage transformation function of buck; Circuit structure is simple, efficient is high, is fit to middle low power (more than the tens of watts of levels) switch voltage-stabilizing or application such as stabilized current power supply, high-brightness LED drive circuit.

Description of drawings

Fig. 1 is existing auto-excitation type Zeta converter circuit figure based on BJT.

Fig. 2 is based on auto-excitation type Zeta converter embodiment 1 circuit diagram of MOSFET.

Fig. 3 is based on auto-excitation type Zeta converter embodiment 2 circuit diagrams of MOSFET.

The input-output voltage characteristic figure of hysteresis comparator U3 among the auto-excitation type Zeta converter embodiment 1 that Fig. 4 is based on MOSFET and the embodiment 2.

Fig. 5 is based on the ideal waveform figure of auto-excitation type Zeta converter embodiment 1 under the inductive current continuous operation mode of MOSFET.

Fig. 6 is based on the ideal waveform figure of auto-excitation type Zeta converter embodiment 2 under the inductive current continuous operation mode of MOSFET.

Embodiment

Below in conjunction with accompanying drawing the present invention is further described.

Embodiment 1

With reference to Fig. 2, Fig. 4 and Fig. 5; A kind of auto-excitation type Zeta converter based on MOSFET; Comprise the Zeta converter major loop of being made up of input capacitance Ci, N type MOSFET M1, inductance L 1, capacitor C, diode D, inductance L 2 and capacitor C o, input capacitance Ci is parallelly connected with direct voltage source Vi, and output capacitance Co voltage is VD Vo; Load Ro is parallelly connected with output capacitance Co; The anode of direct voltage source Vi links to each other with the drain electrode of N type MOSFET M1, and the source electrode of N type MOSFET M1 links to each other with an end of inductance L 1 and an end of capacitor C, and the other end of inductance L 1 links to each other with an end of resistance R 5; The other end of resistance R 5 links to each other with the negative terminal of direct voltage source Vi; The other end of capacitor C links to each other with the negative electrode of diode D and an end of inductance L 2, and the other end of inductance L 2 links to each other with the anode of output voltage V o, and the negative terminal of direct voltage source Vi links to each other with the negative terminal of output voltage V o and the anode of diode D; Said auto-excitation type Zeta converter based on MOSFET also comprises accessory power supply U1, drive circuit U2 and hysteresis comparator U3; Accessory power supply U1 is used to provide drive circuit U2 and the required various DC power supply voltages of hysteresis comparator U3 work; Can boost or the conversion process of step-down to DC input voitage Vi according to actual needs; The input of drive circuit U2 is connected with the output of hysteresis comparator U3; The output of drive circuit U2 links to each other with the gate pole of N type MOSFET M1, and drive circuit U2 is that turning on and off of N type MOSFET M1 (being main switch) provides necessary driving.The input of hysteresis comparator U3 links to each other with an end of capacitor C 1, resistance R 1, resistance R 2 and resistance R 3; The other end of capacitor C 1 and resistance R 3 links to each other with the negative terminal of direct voltage source Vi; The other end of resistance R 1 links to each other with the negative electrode of diode D1; The other end of resistance R 2 links to each other with the anode of diode D2, and the negative electrode of the anode of diode D1 and diode D2 links to each other with the source electrode of N type MOSFET M1.

Shown in Figure 2 is auto-excitation type Cuk converter embodiment 1 based on MOSFET; Adopted the overcurrent protection branch road; Said overcurrent protection branch road comprises resistance R 6, capacitor C 2, NPN type BJTQ2 and positive-negative-positive BJT Q1; One end of resistance R 6 links to each other with the contact of inductance L 1 with resistance R 5; The other end of resistance R 6 links to each other with an end of capacitor C 2 and the base stage of NPN type BJT Q2, and the other end of capacitor C 2 links to each other with the emitter of NPN type BJT Q2 and the negative terminal of direct voltage source Vi, and the collector electrode of NPN type BJT Q2 links to each other with the base stage of positive-negative-positive BJT Q1; The emitter of positive-negative-positive BJT Q1 links to each other with the source electrode of N type MOSFET M1, and the collector electrode of positive-negative-positive BJTQ1 links to each other with the input of hysteresis comparator U3; Also adopted the Voltage Feedback branch road; Said Voltage Feedback branch road comprises resistance R 7, capacitor C 3, resistance R 8, NPN type BJT Q3, resistance R 4 and positive-negative-positive BJT Q1; Resistance R 7 is formed parallel branch with capacitor C 3; One end of said parallel branch links to each other with the anode of VD Vo; The other end of said parallel branch links to each other with an end of resistance R 8 and the base stage of NPN type BJT Q3, and the emitter of NPN type BJT Q3 links to each other with the other end of resistance R 8 and the negative terminal of direct voltage source Vi, and the collector electrode of NPN type BJT Q3 links to each other with the base stage of positive-negative-positive BJT Q1 through resistance R 4.

In the present embodiment, overcurrent protection branch road and Voltage Feedback branch road can shared positive-negative-positive BJTQ1.Certainly, also can only adopt overcurrent protection branch road or Voltage Feedback branch road.

The ideal waveform figure of auto-excitation type Zeta converter embodiment 1 under the inductive current continuous operation mode based on MOSFET shown in Figure 5.Its circuit working principle is specific as follows:

(1) the circuit electrifying startup stage: after circuit powered on, accessory power supply U1 started working, and converted DC input voitage Vi to drive circuit U2 and the required voltage of hysteresis comparator U3 work.Subsequently, drive circuit U2 and hysteresis comparator U3 also start working.Just having begun is t=t0, and the terminal voltage vc1 of capacitor C 1 is zero, and because of the lower limit reference voltage Vref 1 of vc1 less than U3, U3 output vp high level is through U2 level conversion output vgs1 high level, M1 conducting.After the M1 conducting, diode D ends, and forms the loop by Vi, Ci, M1, L1, R5; Form another loop by Vi, Ci, M1, C, L2, Co, Ro, inductance L 1 increases with L2 charging, inductive current iL1, iL2; The capacitor C reverse charging, output capacitance Co positive charge, voltage vs1 equals Vi.Simultaneously, C1 is through D1 and R1 charging, and voltage vc1 rises.The upper limit reference voltage Vref 2 that rises to U3 as vc1 is t=t1, U3 output vp low level, and through U2 level conversion output vgs1 low level, M1 turn-offs.M1 closes and has no progeny, and the D conducting forms the loop by C, L1, R5, D, forms another loop by L2, Co, Ro, D, capacitor C and Co positive charge, and inductance L 1 and L2 discharge, inductive current iL1 and iL2 reduce, and voltage vs1 equals-vc, and output voltage vo rises.C1 is through D2 and R2 discharge simultaneously, and voltage vc1 descends.The lower limit reference voltage Vref 1 that drops to U3 as vc1 is t=t2, U3 output vp high level, and through U2 level conversion output vgs1 high level, M1 is conducting once more, and circuit gets into next from flyback cycle.Go through several cycles, after the output voltage of circuit reached set point Vo, circuit had just been accomplished the electrifying startup process, got into 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 was higher than set point Vo, the Q3 conducting was shortened the ON time (being t4-t3) of M1 through the charging current that strengthens capacitor C 1, realizes the reduction of output voltage.When output voltage was lower than set point Vo, Q3 turn-offed, and the basic self-excitation element circuit of single MOSFET works alone, and the ON time of M1 recovers former state again, realized the lifting of output voltage.Thus, circuit can realize exporting voltage stabilizing.

Behind embodiment 1 circuit working, no matter be starting state or steady operation state, as long as overcurrent appears in L1, the overcurrent protection branch road will work.When R5, R6 and C2 detect the L1 overcurrent, Q2 and Q1 conducting immediately, moment is strengthened the charging current of capacitor C 1, treats that vc1 rises rapidly and the upper limit reference voltage Vref 2 back M1 that are higher than U3 will turn-off, and stops that electric current continues to increase among the L1.

Embodiment 2

With reference to Fig. 3, Fig. 4 and Fig. 6; Present embodiment also comprises the current feedback branch road; Said current feedback branch road comprises detection resistance R 9, voltage amplifier U4, resistance R 7, capacitor C 3, resistance R 8, NPN type BJT Q3, resistance R 4 and positive-negative-positive BJT Q1; Detect resistance R 9 and form series arm with load Ro, said series arm is parallelly connected with output capacitance Co, and an end that detects resistance R 9 links to each other with the negative terminal of direct voltage source Vi; The other end that detects resistance R 9 links to each other with the end of load Ro and the input of voltage amplifier U4; Resistance R 7 is formed parallel branch with capacitor C 3, and an end of said parallel branch links to each other with the output of voltage amplifier U4, and the other end of said parallel branch links to each other with an end of resistance R 8 and the base stage of NPN type BJT Q3; The emitter of NPN type BJT Q3 links to each other with the other end of resistance R 8 and the negative terminal of direct voltage source Vi; The collector electrode of NPN type BJT Q3 links to each other with the base stage of positive-negative-positive BJT Q1 through resistance R 4, and the emitter of positive-negative-positive BJT Q1 links to each other with the source electrode of N type MOSFET M1, and the collector electrode of positive-negative-positive BJT Q1 links to each other with the input of hysteresis comparator U3.

Among the present invention, overcurrent protection branch road and current feedback branch road can shared positive-negative-positive BJTQ1.Certainly, also can only adopt overcurrent protection branch road or current feedback branch road.

The circuit working principle of present embodiment is specific as follows:

(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 accomplished the electrifying startup process, got into 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 was higher than set point Io, the Q3 conducting was shortened the ON time (being t4-t3) of M1 through the charging current that strengthens capacitor C 1, realizes the reduction of output current.When output current was lower than set point Io, Q3 turn-offed, and the basic self-excitation element circuit of single MOSFET works alone, and the ON time of M1 recovers former state again, realized the lifting of output current.Thus, circuit can realize exporting current stabilization.

Other circuit structures of present embodiment are identical with embodiment 1.

The described content of this specification embodiment only is enumerating the way of realization of inventive concept; Should not being regarded as of protection scope of the present invention only limits to the concrete form that embodiment states, protection scope of the present invention also reach in those skilled in the art conceive according to the present invention the equivalent technologies means that can expect.

Claims

1. A self-excited Zeta converter based on MOSFET is characterized in that: it comprises a Zeta converter main circuit composed of input capacitor Ci, N-type MOSFET M1, inductor L1, capacitor C, diode D, inductor L2 and capacitor Co , the input capacitor Ci is connected in parallel with the DC voltage source Vi, the voltage across the output capacitor Co is the DC output voltage Vo, the load Ro is connected in parallel with the output capacitor Co, the positive terminal of the DC voltage source Vi is connected to the drain of the N-type MOSFET M1, and the N-type The source of MOSFET M1 is connected to one end of inductor L1 and one end of capacitor C, the other end of inductor L1 is connected to one end of resistor R5, the other end of resistor R5 is connected to the negative end of DC voltage source Vi, and the other end of capacitor C is connected to The cathode of the diode D is connected to one end of the inductor L2, the other end of the inductor L2 is connected to the positive end of the output voltage Vo, and the negative end of the DC voltage source Vi is connected to the negative end of the output voltage Vo and the anode of the diode D;

The self-excited Zeta converter based on MOSFET also includes an auxiliary power supply U1, a drive circuit U2 and a hysteresis comparator U3, and the auxiliary power supply U1 is used to provide the DC supply voltage required for the work of the drive circuit U2 and the hysteresis comparator U3, Step-up or step-down conversion processing is performed on the DC input voltage Vi; the input terminal of the drive circuit U2 is connected to the output terminal of the hysteresis comparator U3, the output terminal of the drive circuit U2 is connected to the gate of the N-type MOSFET M1, and the drive circuit U2 provides drive for the turn-on and turn-off of N-type MOSFET M1; the input terminal of hysteresis comparator U3 is connected to one end of capacitor C1, resistor R1, resistor R2 and resistor R3, and the other end of capacitor C1 and resistor R3 is connected to a DC voltage source The negative end of Vi is connected, the other end of resistor R1 is connected to the cathode of diode D1, the other end of resistor R2 is connected to the anode of diode D2, the anode of diode D1 and the cathode of diode D2 are connected to the source of N-type MOSFET M1.

2. The self-excited Zeta converter based on MOSFET as claimed in claim 1 is characterized in that: the self-excited Zeta converter based on MOSFET also includes an overcurrent protection branch, and the overcurrent protection branch includes a resistor R6, capacitor C2, NPN type BJT Q2 and PNP type BJT Q1, one end of resistor R6 is connected to the junction of inductor L1 and resistor R5, the other end of resistor R6 is connected to one end of capacitor C2 and the base of NPN type BJT Q2, and the capacitor The other end of C2 is connected to the emitter of the NPN BJT Q2 and the negative terminal of the DC voltage source Vi, the collector of the NPN BJT Q2 is connected to the base of the PNP BJT Q1, and the emitter of the PNP BJT Q1 is connected to the N-type MOSFET The source of M1 is connected, and the collector of PNP type BJT Q1 is connected with the input terminal of hysteresis comparator U3.

3. The self-excited Zeta converter based on MOSFET as claimed in claim 1 is characterized in that: the self-excited Zeta converter based on MOSFET also includes a voltage feedback branch, and the voltage feedback branch includes resistor R7, Capacitor C3, resistor R8, NPN type BJT Q3, resistor R4, PNP type BJT Q1, resistor R7 and capacitor C3 form a parallel branch, one end of the parallel branch is connected to the positive end of the DC output voltage Vo, and the parallel branch The other end of the circuit is connected to one end of the resistor R8 and the base of the NPN BJT Q3, the emitter of the NPN BJT Q3 is connected to the other end of the resistor R8 and the negative end of the DC voltage source Vi, and the collector of the NPN BJT Q3 passes through The resistor R4 is connected to the base of the PNP BJT Q1, the emitter of the PNP BJT Q1 is connected to the source of the N-type MOSFET M1, and the collector of the PNP BJT Q1 is connected to the input terminal of the hysteresis comparator U3.

4. The self-excited Zeta converter based on MOSFET as claimed in claim 1, characterized in that: the self-excited Zeta converter based on MOSFET also includes a current feedback branch, and the current feedback branch includes a detection resistor R9 , voltage amplifier U4, resistor R7, capacitor C3, resistor R8, NPN type BJT Q3, resistor R4 and PNP type BJT Q1, the detection resistor R9 and the load Ro form a series branch, and the series branch is connected in parallel with the output capacitor Co to detect One end of the resistor R9 is connected to the negative end of the DC voltage source Vi, the other end of the detection resistor R9 is connected to one end of the load Ro and the input end of the voltage amplifier U4, the resistor R7 and the capacitor C3 form a parallel branch, and the parallel branch One end is connected to the output end of the voltage amplifier U4, the other end of the parallel branch is connected to one end of the resistor R8 and the base of the NPN BJT Q3, and the emitter of the NPN BJT Q3 is connected to the other end of the resistor R8 and the DC voltage source The negative terminal of Vi is connected, the collector of NPN BJT Q3 is connected to the base of PNP BJT Q1 through resistor R4, the emitter of PNP BJT Q1 is connected to the source of N-type MOSFET M1, and the collector of PNP BJT Q1 It is connected with the input end of hysteresis comparator U3.

5. The self-excited Zeta converter based on MOSFET as claimed in claim 2 is characterized in that: the self-excited Zeta converter based on MOSFET also includes a voltage feedback branch, and the voltage feedback branch includes resistor R7, Capacitor C3, resistor R8, NPN type BJT Q3 and resistor R4, resistor R7 and capacitor C3 form a parallel branch, one end of the parallel branch is connected to the positive end of the DC output voltage Vo, and the other end of the parallel branch is connected to One end of the resistor R8 is connected to the base of the NPN type BJT Q3, the emitter of the NPN type BJT Q3 is connected to the other end of the resistor R8 and the negative end of the DC voltage source Vi, and the collector of the NPN type BJT Q3 is connected to the PNP type via the resistor R4. The base of BJT Q1 is connected.

6. The self-excited Zeta converter based on MOSFET as claimed in claim 2 is characterized in that: the self-excited Zeta converter based on MOSFET also includes a current feedback branch, and the current feedback branch includes a detection resistor R9 , voltage amplifier U4, resistor R7, capacitor C3, resistor R8, NPN type BJT Q3 and resistor R4, detection resistor R9 and load Ro form a series branch, the series branch is connected in parallel with the output capacitor Co, one end of the detection resistor R9 is connected to The negative end of the DC voltage source Vi is connected, the other end of the detection resistor R9 is connected to one end of the load Ro and the input end of the voltage amplifier U4, the resistor R7 and the capacitor C3 form a parallel branch, and one end of the parallel branch is connected to the voltage amplifier U4 The other end of the parallel branch is connected to one end of the resistor R8 and the base of the NPN BJT Q3, and the emitter of the NPN BJT Q3 is connected to the other end of the resistor R8 and the negative end of the DC voltage source Vi , the collector of the NPN type BJT Q3 is connected to the base of the PNP type BJT Q1 through the resistor R4.