CN101399502A - Forward Converter with Self-Driven Synchronous Rectifier - Google Patents

Abstract

A forward converter with a self-driven synchronous rectifier uses a secondary drive coil and a secondary drive circuit to drive the synchronous rectifier in a secondary power circuit. The secondary drive circuit includes a potential shifter and a signal distributor, which shifts the voltage across the secondary drive coil by a potential and distributes the voltage signal to control the forward and unconstrained rectifiers to reduce conduction losses. In particular, the unconstrained rectifier can still be turned on during the delay period to further reduce conduction losses.

Description

Forward Converter with Self-Driven Synchronous Rectifier

technical field

The present invention discloses a forward converter with a self-driven synchronous rectifier.

Background technique

Forward converters are often used to convert a high DC voltage source into multiple sets of low DC voltage sources, where the master output is modulated with a closed-loop pulse width modulation ) voltage regulation (regulated) while the slave outputs (slave outputs) are regulated by a secondary side post regulator (SSPR).

The main output circuit is shown in Figure 1. The secondary power circuit is composed of a secondary power coil T _s , a forward rectifier M _f , a freewheeling rectifier M _w , an energy storage inductor L ₁ and a filter capacitor C ₁ . In this circuit, the error amplifier circuit 3 samples the output voltage _V1 and compares it with a reference voltage to generate an amplified error voltage; the control circuit 2 converts the amplified error voltage into a pulse width modulation signal; the drive circuit 1 The pulse width modulation signal is converted into a driving signal for the forward rectifier M _f and the unconstrained rectifier M _w . When the forward rectifier M _f is turned on and the unconstrained rectifier M _w is turned off, the voltage V _L1 of the energy storage inductor L ₁ is positive, and the energy storage inductor L ₁ passes through the forward rectifier M _f , the secondary power coil T _s and the filter capacitor _C1 stores electrical energy. When the forward rectifier _Mf is turned off and the unconstrained rectifier _Mw is turned on, the voltage V _L1 of the energy storage inductor _L1 is negative, and the energy storage inductor _L1 releases electric energy through the unconstrained rectifier _Mw and the filter capacitor _C1 . This kind of circuit structure (also called separately driven synchronous rectifier) is relatively complicated and expensive.

The slave output circuit is shown in Figure 2. The secondary power circuit is composed of secondary power coil T _s2 , secondary post-regulator S ₁ , forward diode rectifier D _f , unconstrained diode rectifier D _w , energy storage inductor L ₂ and filter capacitor C ₂ ; among them, the secondary The post-stage regulator S ₁ is used to blank the leading edge of the voltage waveform across the secondary power coil T _s2 so that the input voltage waveform of the energy storage inductor L ₂ (connecting D _f , D _w and L ₂ node to ground) is the output voltage V ₂ .

The shadowing effect of the secondary post-regulator S1, as shown in Figure 3, can be explained by the voltage waveforms of the energy storage inductor _L1 of the main output and the energy storage inductor _L2 of the slave output. During the turn-on period 0<t<T _on , the voltage waveform V _L1 of the energy storage inductor L ₁ is not shielded and is positive (energy storage). During the blanking period 0<t<T _blank , since the secondary post-regulator S ₁ is turned off, no current flows through the forward diode rectifier D _f . The continuous current of the energy storage inductor _L2 forces the unconstrained diode rectifier _Dw to conduct so that its voltage waveform V _L2 is negative (discharged). During the non-blocking period T _blank <t<T _on , since the secondary post-regulator S ₁ is turned on, the forward diode rectifier D _f starts to conduct current. The continuous current of the energy storage inductor L2 is commutated from the unfettered diode rectifier _Dw to the forward diode rectifier _Df such that its voltage waveform V _L2 is positive (energy storage).

The secondary post regulator S ₁ can be a magnetic amplifier (MA) or a controlled switch. When implementing the secondary post-regulator _S1 with a magnetic amplifier, a reset circuit needs to be connected. If the secondary post-regulator S ₁ is implemented with a controlled switch, an IC driver needs to be connected. Here, the reset circuit and the integrated circuit driver are collectively referred to as the switch controller 4 .

It is worth noting that the rectifier of the slave circuit uses a diode as the rectifier of the power circuit, which causes a large conduction loss of the rectifier.

Contents of the invention

Therefore, in order to solve the above problems, it is an object of the present invention to provide a cost-effective forward converter with self-driven synchronous rectifiers to simultaneously drive the synchronous rectifiers in the master and slave loops.

According to one aspect of the present invention there is provided a forward converter having a self-driven synchronous rectifier, wherein the main output circuit utilizes a drive circuit connected to a secondary drive coil of a transformer to drive power connected to a secondary power coil Forward rectifiers and unconstrained rectifiers for loops. The driving circuit also includes a potential shifter, which makes the voltage across the secondary driving coil generate a potential displacement, and then outputs it as a voltage signal. After receiving the voltage signal, the signal distributor can distribute the voltage signal to the control terminals of the forward rectifier and the unconstrained rectifier.

According to another aspect of the present invention, there is provided a forward converter with a self-driven synchronous rectifier, wherein the slave output circuit includes a secondary post-regulator serially connected to the slave secondary power coil, a slave power circuit, a slave secondary Driving coil and a driving circuit. The slave power circuit is used to provide the slave output voltage, and the drive circuit is connected to the slave secondary drive coil to turn on or off the forward rectifier of the slave power circuit, and the control terminal of the unconstrained rectifier of the slave power circuit receives the power of the main output The voltage signal of the unconstrained rectifier of the loop, while simultaneously turning on or off. The secondary post-regulator is a magnetic amplifier or a controlled switch used to mask the leading edge of the voltage waveform across the secondary power coil to adjust its output voltage.

Description of drawings

FIG. 1 is a schematic diagram of a main output circuit of a conventional forward converter.

FIG. 2 is a schematic diagram of a slave output circuit of a conventional forward converter.

FIG. 3 is a waveform diagram of input terminal voltages of energy storage inductors of the main output circuit and the slave output circuit of the conventional forward converter.

FIG. 4 is a schematic diagram of a main output circuit of a forward converter with a self-driven rectifier according to an embodiment of the present invention.

FIG. 5 is a main output circuit diagram of a forward converter with a self-driven rectifier according to an embodiment of the present invention.

FIG. 6 is a waveform diagram of the gate voltage of the secondary drive coil, the forward transistor of the main output circuit, and the gate voltage of the unconstrained transistor within one period of the embodiment shown in FIG. 5 .

FIG. 7 is a schematic diagram of a main output circuit of a forward converter with a self-driven rectifier according to an embodiment of the present invention.

FIG. 8 is a main output circuit diagram of a forward converter with a self-driven rectifier according to an embodiment of the present invention.

FIG. 9 is the embodiment shown in FIG. 8 , a waveform diagram of the first secondary drive coil, the gate voltage of the forward transistor of the main output circuit, and the gate voltage of the unconstrained transistor within one cycle.

FIG. 10 is a schematic diagram of a slave output circuit of a self-driven forward converter according to an embodiment of the present invention.

11 and 12 are the slave output circuit diagrams of the self-driven forward converter according to different embodiments of the present invention.

Fig. 13 is the embodiment of the slave output circuit shown in Fig. 11, with the embodiment of the master output shown in Fig. 5, within one cycle, the gate voltage of the secondary drive coil, the forward transistor of the slave output and Gate voltage waveform diagram of a transistor.

Fig. 14 is an embodiment of the slave output circuit shown in Fig. 11, which is matched with the embodiment of the main output shown in Fig. 8; Gate voltage waveform diagram of a constrained transistor.

Detailed ways

Please refer to FIG. 4 , which is a schematic diagram of a main output configuration of a forward converter with a self-driven synchronous rectifier according to an embodiment of the present invention. As shown in the figure, a transformer includes a primary winding (primary winding) T ₁ , a secondary power winding (secondary power winding) T ₂ and a secondary driving winding (secondary driving winding) T ₃ , wherein the primary winding T ₁ is used to connect to an external power supply , to provide the input voltage Vi, the black dot end in the figure is the first end of the coil, the black dot indicates the same polarity, and the other end is the second end of the coil.

The secondary power coil T ₂ is connected to the main power circuit 21 and has a voltage output terminal (high voltage terminal) and a ground terminal (low voltage terminal) to provide a voltage V ₁ for driving an external load circuit (load) (not shown in the figure). A filter capacitor C ₃ is connected across the voltage output terminal and the ground terminal for voltage stabilization, and the first terminal (black dot terminal) of the secondary power coil T ₂ and the voltage output terminal are connected in series with an energy storage inductor L ₃ .

The main power circuit 21 includes a forward rectifier 211, a freewheeling rectifier 212 and an energy storage inductor L ₃ , wherein the forward rectifier 211 and the freewheeling rectifier 212 include a first terminal, a second terminal and a control terminal, and the control terminal receives The voltage signal is used to switch on or off the circuit between the first terminal and the second terminal. As shown in the figure, the first ends of the forward rectifier 211 and the unconstrained rectifier 212 are respectively connected to the two ends of the secondary power coil T ₂ , the second ends of the two rectifiers 211, 212 are connected to each other at the connection point Z _M , and connected to Point Z _M is connected to ground.

Secondly, the two ends of the secondary drive coil _T3 are connected to the first output end and the second output end of the signal distributor 22, and the common connection end of the signal distributor 22 is connected to the connection point Z of the second ends of the two rectifiers 211 and 212. _M , the first output terminal and the second output terminal are respectively connected to the control terminals of the unconstrained rectifier 212 and the forward rectifier 211 .

When the voltage value (voltage signal) of the first end (black dot end) of the secondary driving coil _T3 is positive, the first output end of the conduction signal distributor 22 is conducted with the common connection end, and the voltage signal is distributed To the control end of the forward rectifier 211 connected to the second output end of the signal distributor 22, when the voltage value of the first end (black dot end) of the secondary drive coil _T3 is negative, the signal distributor 22 is turned on The second output terminal of the second output terminal of the signal distributor 22 is connected to the common connection terminal, and the voltage signal is distributed to the control terminal of the unconstrained rectifier 212 connected to the first output terminal of the signal distributor 22 .

FIG. 5 is an implementation circuit diagram of the main output of the forward converter with the self-driven synchronous rectifier according to the embodiment of FIG. 4 . As shown in the figure, the forward rectifier 211 and the unconstrained rectifier 212 are realized by two transistors M ₁ and M ₂ , which are called forward transistor M ₁ and unconstrained transistor M ₂ respectively. In this embodiment, the drains of the transistors M ₁ and M ₂ serve as the first terminal of the forward rectifier, the source serves as the second terminal, and the gate serves as the control terminal.

Furthermore, the signal distributor 22 includes two diodes D ₁ and D ₂ connected back to back, that is, the anodes of the two diodes are connected, and the connection point thereof is used as a common connection terminal, and the cathodes of the diodes D ₁ and D ₂ are respectively used as the first output terminal and the second output terminal are respectively connected to the gates (control terminals) of the unconstrained transistor _M2 and the forward transistor _M1 .

Fig. 6 illustrates the voltage timing (voltage waveform) of the first terminal of the secondary driving coil _T3 , the gate of the forward transistor _M1 and the gate of the unconstrained transistor _M2 in the embodiment shown in Fig. 5 within one cycle picture. For the convenience of description, in this embodiment, the voltage across the two terminals of the secondary driving coil T ₃ is V _s .

During the turn-on period 0<t<T _on , the voltage at the first terminal of the secondary drive coil T ₃ is V _s (positive value), the diode D ₁ is turned on by the forward bias voltage, and the diode D ₂ is turned off by the reverse bias voltage . The signal distributor 22 distributes the voltage signal (voltage V _s ) to the gate (control terminal) of the forward transistor _M1 to be turned on, and the gate (control terminal) of the unconstrained transistor _M2 is turned off by the voltage 0. During this period, the energy storage inductor L ₃ stores electric energy through the forward transistor M ₁ , the secondary power coil T ₂ and the filter capacitor C ₃ .

During the reset period T _on ≤t≤T _on +T _reset , the voltage at the first terminal of the secondary driving coil T ₃ is -V _s (negative value), the diode D ₁ is turned off by reverse bias, and the diode D ₂ is turned off by forward biased to turn on. The signal distributor 22 distributes the voltage signal (voltage V _s ) to the gate (control terminal) of the unconstrained transistor _M2 to turn on, and the gate (control terminal) of the forward transistor _M1 receives the voltage 0 to turn off. During this period, the energy storage inductor L ₃ releases electric energy through the unconstrained transistor M ₂ and the filter capacitor C ₃ .

During the delay period T _on + T _reset ≤ t ≤ _{T s} , the voltage across the two terminals of the secondary driving coil T ₃ is 0, and the diodes D ₁ and D ₂ are both turned off. The gates of the forward transistor _M1 and the unrestrained transistor _M2 are both turned off by the voltage 0. During this period, the continuous current of the energy storage inductor L ₃ forces the body diode of the unconfined transistor M ₂ to conduct and discharge the energy through the filter capacitor C ₃ .

It should be noted that the continuous current of the energy storage inductor L ₃ flows through the body diode of the unconfined transistor M ₂ during the delay period T _on +T _reset ≤ t ≤ T _s . The conduction loss can be further reduced with a potentiometer. The embodiment shown in FIG. 7 is a schematic circuit diagram of the configuration circuit of the main output of the forward converter with self-driven synchronous rectifier in the embodiment of the present invention having the potential shifter 23 . Comparing this embodiment with the embodiment shown in FIG. 4 , the difference is that a potential shifter 23 is added in this embodiment to further reduce the conduction loss during the delay period.

As shown in the figure, the potentiometer 23 has a first input terminal, a second input terminal, a first output terminal and a second output terminal. In this embodiment, the second output terminal and the second input terminal are the same terminal. The first end and the second end of the secondary driving coil _T3 are connected to the first input end and the second input end of the potential shifter 23, and the first output end and the second output end of the potential shifter 23 are connected across the driving signal The first output end and the second output end of the distributor 22 .

In particular, the two output terminals of the potential shifter 23 have shifted the potentials of the two input terminals by a voltage displacement V _r . For example, in this embodiment, the voltage signal output by the secondary drive coil _T3 is V _s , and the potential displacement V _r of the potential shifter 23, so the voltage signals distributed by the signal distributor 22 are respectively the first voltage signal of the potential shifter 23. The voltage V _s -V _r at the output terminal and the voltage -V _s -V _r at the second output terminal.

FIG. 8 is an implementation circuit diagram of the main output of the forward converter with the self-driven synchronous rectifier according to the embodiment of FIG. 7 . As shown in the figure, the potentiometer 23 includes a capacitor C ₄ , a diode D ₄ and a Zener diode ZD ₄ connected in series. One end of the capacitor _C4 is used as the first input end, one end is connected to the anode of the diode _D4 , the connection point is used as the first output end, the cathode of the diode _D4 is connected to the cathode of the Zener diode _ZD4 , and the anode of the Zener diode _ZD4 is simultaneously used as The second input end and the second output end. The operating principle of the potentiometer 23 of this embodiment will be described below.

During the turn-on period 0<t<T _on , the diode _D4 of the potentiometer 23 is turned on, and the secondary driving coil _T3 charges the capacitor _C4 , wherein the capacitance value of the capacitor _C4 is within a switching period (switching period) , can maintain a constant transvoltage V _c4 , and the forward voltage drop V _f of the diode D ₄ is extremely small. For the sake of simplicity, the forward voltage drop V _f is assumed to be zero in this embodiment. Therefore, the voltage V _c4 across the capacitor C ₄ is the potential displacement V _r provided by the potentiometer 23, which can be expressed as V _c4 =V _s -V _z -V _f =V _s -V _z , where V _s is the positive driving voltage of the secondary driving coil _T3 , _Vz is the breakdown voltage of the Zener diode _ZD4 , and the forward voltage drop _Vf of the diode _D4 has been assumed to be 0.

FIG. 9 illustrates a timing diagram of the voltages at the first terminal of the secondary driving coil _T3 , the gate of the forward transistor _M1 and the gate of the unconstrained transistor _M2 in the embodiment shown in FIG. 8 within one cycle.

During the turn-on period 0≤t≤T _on , the difference from the embodiment in FIG. 6 is that the voltage signal distributed to the gate of the forward transistor M ₁ is V _z =V _s −(V _s −V _z ).

During the reset period T _on ≤ t ≤ T _on +T _reset , the difference from the embodiment in FIG. 6 is that the voltage signal distributed to the gate of the unconstrained transistor M ₂ is 2V _s -V _z =V _s +(V _s - V _z ).

During the delay period T _on +T _reset ≤t≤T _s , the difference from the embodiment in Figure 6 is that the gate of the unconstrained transistor M ₂ is still assigned the voltage signal V _s -V _z , therefore, during this period, the unconstrained transistor M 2 M ₂ is still turned on, and the energy storage inductor L ₃ releases electric energy through the unconstrained transistor M ₂ and the filter capacitor C ₃ to further reduce the conduction loss.

Please refer to FIG. 10 to illustrate a schematic diagram of a slave output circuit according to an embodiment of the present invention. As shown in the figure, the first end (black dot end) of the secondary power coil _T14 is connected in series with the secondary post-regulator _S2 and the subordinate power circuit, the output end of the subordinate power circuit includes the auxiliary voltage output end and the ground end, and The slave filter capacitor C ₅ is connected across the slave voltage output terminal and the ground terminal, wherein the slave voltage output terminal provides the slave output voltage V ₂ . The secondary driving coil T ₁₃ is connected to the driving circuit 32 for driving the secondary power circuit.

The secondary power circuit includes a forward rectifier 311 , an unconstrained rectifier 312 and an energy storage inductor L ₅ . The second end of the forward rectifier 311 is connected to the secondary post-regulator S ₂ , the first end of the forward rectifier 311 is connected to the first end of the unconstrained rectifier 312 at the connection point Z _s , and the connection point Z _s is connected to the auxiliary voltage output The energy storage inductor L ₅ is connected in series between the terminals. The second terminal of the unconstrained rectifier 312 is connected to the second terminal of the secondary power coil _T14 and connected to the ground terminal, and the control terminal of the unconstrained rectifier 312 is connected to the control terminal of the unconstrained rectifier of the main output circuit, thereby receiving its voltage signal. Wherein, the secondary post regulator S ₂ is connected to a switch controller 33 .

The drive circuit 32 is connected to the secondary drive coil _T13 and the control terminal of the forward rectifier 311 of the subordinate power circuit, to provide the voltage signal of the control terminal of the forward rectifier 311, and the second terminal of the secondary drive coil _T13 is connected to forward to the second end of the rectifier 311 .

FIG. 11 is a practical circuit diagram of the embodiment shown in FIG. 10 . The forward rectifier 311 and the unconstrained rectifier 312 using transistors M ₇ and M ₈ as the slave output circuit are respectively referred to as the forward transistor M ₇ and the unconstrained transistor M ₈ , wherein the drain, source and gate of the transistors are respectively As the first terminal, the second terminal and the control terminal of the rectifier.

The driving circuit 32 includes a diode _D7 and an interlock switching circuit connected to the secondary driving coil _T13 and the gate of the forward transistor _M7 . The interlock switching circuit includes an NPN bipolar transistor Q ₁ , a PNP bipolar transistor Q ₂ , and two resistors R ₁ and R ₂ . Transistor _Q1 is connected to the emitter of transistor _Q2 , and the connection point is connected to the gate of forward transistor _M7 . The bases of the two transistors Q ₁ and Q ₂ are connected, and the connection point of the bases and the collectors of the transistors Q ₁ and Q ₂ are respectively connected with resistors R ₁ and R ₂ . The collectors of the transistors Q ₁ and Q ₂ are respectively connected to the cathode of the diode D ₇ and the second end of the secondary driving coil T ₁₃ , and the anode of the diode D ₇ is connected to the first end of the secondary driving coil T ₁₃ .

When the voltage at the first terminal of the secondary driving coil T ₁₃ is V _s2 (positive value), the transistor Q ₁ is turned on and the transistor Q ₂ is turned off so that the forward transistor M ₇ is turned on. When the voltage at the first terminal of the secondary driving coil T ₁₃ is -V _s2 (negative value) or 0, the transistor Q ₁ is turned off and the transistor Q ₂ is turned on so that the forward transistor M ₇ is turned off. Because the gate-source voltage waveform of the forward transistor _M7 is nonnegative, this driving mode is called unipolar driving mode.

FIG. 12 is another implementation circuit diagram of the embodiment shown in FIG. 10 , which differs from the embodiment shown in FIG. 11 in that a bipolar driving mode is adopted. As shown in the figure, the driving circuit 32 only includes two connected resistors R ₁ , R ₂ , which are respectively connected to the first terminal and the second terminal of the secondary driving coil T ₁₃ . The connection point of the resistors R ₁ and R ₂ is connected to the gate of the forward transistor M ₇ , and the resistor R ₂ is connected between the gate and the source of the forward transistor M ₇ .

When the voltage at the first terminal of the secondary driving coil T ₁₃ is V _s2 (positive value), the divided voltage of the resistors R ₁ and R ₂ is positive, and the forward transistor M ₇ is thus turned on. When the voltage at the first terminal of the secondary driving coil T ₁₃ is -V _s2 (negative value) or 0, the divided voltage of R ₁ and R ₂ is nonpositive, and the forward transistor M ₇ is turned off.

When the secondary post-regulator _S2 is a controlled switch, the gate of the forward transistor _M7 of the slave power circuit can be connected to the gate of the forward transistor of the main output circuit to receive its voltage signal, and the drive circuit 32 is omitted , to further simplify the circuit. Furthermore, the forward transistor _M7 can be moved to the second terminal of the secondary power coil _T14 to adopt a common-source configuration with the unconstrained transistor _M8 . That is to say, the second end of the forward rectifier and the unconstrained rectifier of the subordinate power circuit are connected to the ground end, and the first end is respectively connected to one end of the secondary circuit coil _T1 and the secondary post-regulator _S2 . The control terminal respectively receives the voltage signals of the forward rectifier and the control terminal of the unconstrained rectifier of the power circuit of the main output circuit, and the rest of the circuit is the same as the foregoing embodiment.

Fig. 13 is a period, the embodiment shown in Fig. 11 is the first end of the secondary driving coil T ₁₃ of the slave output, the gate (control end) voltage sequence of the forward transistor M ₇ and the unconstrained transistor M ₈ ( Voltage waveform) figure, the main output circuit of the present embodiment is the embodiment shown in Figure 5.

During the turn-on period 0≤t≤T _on , the voltage at the first terminal of the secondary drive coil T ₁₃ is V _s2 (positive value), the gate of the forward transistor M ₇ is turned on by the voltage V _s2 , and the gate of the unconstrained transistor M ₈ The pole accepts the gate voltage signal (voltage 0) of the unconstrained transistor _M2 in the main output circuit and turns off. The shadowing effect of the secondary post-regulator _S2 on the leading edge of the voltage waveform of the secondary power coil _T14 is shown in the shadowed area in FIG. 13 . During the blank period 0<t<T _blank , since the secondary post-regulator _S2 is turned off, no current flows through the forward transistor _M7 even though it is turned on. The continuous current of the energy storage inductor _L5 forces the body diode of the unconfined transistor _M8 to conduct and discharge the energy through the filter capacitor _C5 . During the non-blocking period T _blank <t<T _on , since the secondary post-regulator S ₂ is turned on, the forward transistor M ₇ starts to conduct current, and the continuous current of the energy storage inductor L ₅ is switched from the body diode of the unconstrained transistor M ₈ It flows to the forward transistor _M7 and stores electrical energy through the forward transistor _M7 , the secondary post-regulator _S2 , the secondary power coil _T14 and the filter capacitor _C5 .

During the reset period T _on ≤ t ≤ T _on +T _reset , the voltage at the first terminal of the secondary driving coil T ₁₃ is -V _s2 (negative value). The gate-source voltage of forward transistor _M7 is 0 (unipolar driving) or negative (bipolar driving) and turned off. The gate of the unstrained transistor _M8 is turned on following the gate voltage _Vs of the unstrained transistor _M2 in the main output circuit. The energy storage inductor L ₅ releases electric energy through the unconstrained transistor M ₈ and the filter capacitor C ₅ .

During the delay period T _on + T _reset ≤ t ≤ _{T s} , the voltage across the two terminals of the secondary driving coil T ₁₃ is 0, and the gate voltage of the forward transistor M ₇ is 0 and turned off. The gate of unconfined transistor _M8 is turned off following the gate voltage 0 of unconfined transistor _M2 in the main output circuit. The energy storage inductor L ₅ releases electric energy through the body diode of the unconstrained transistor M ₈ and the filter capacitor C ₅ .

Fig. 14 is the gate (control terminal) voltage sequence of the first end of the secondary drive coil T ₁₃ , the forward transistor M ₇ and the unconstrained transistor M ₈ in the embodiment shown in Fig. 11 within one cycle (Voltage Waveform) Figure, the main output circuit of this embodiment is the embodiment shown in Figure 8. The difference from the embodiment shown in FIG. 13 is that during the reset period and the delay period, the gate of the unconstrained transistor _M8 accepts the gate voltage of the unconstrained transistor of the main output circuit, wherein the accepted voltage value during the reset period is 2V _s -V _z , and V _s -V _z during the delay period. It should be noted that during the delay period, the gate voltage of the unconstrained transistor M ₈ is turned on with a positive value, which further reduces the conduction loss.

In particular, it should be noted that the unconstrained transistor and the forward transistor in the above embodiment can be an N-channel MOSFET, a P-channel MOSFET, an N-channel junction transistor, or a P-channel transistor. The channel junction field effect transistor, the present invention is not limited to the above.

The above-described embodiments are only for illustrating the technical ideas and characteristics of the present invention, and its purpose is to enable those familiar with the art to understand the content of the present invention and implement it accordingly. When it cannot limit the patent scope of the present invention, that is, All equivalent changes or modifications made according to the spirit disclosed in the present invention shall still fall within the patent scope of the present invention.

Claims (11)

1. forward converter with self-driven synchronous rectifier comprises:

One transformer has a primary coil, a level drive coil and a level power line circle, and wherein this primary coil connects an external power source;

One main power circuit, comprise a rectifier forward, one does not have a constraint rectifier and an energy storage inductor, this secondary power lines circle that connects this transformer, wherein this main power circuit has a principal voltage output and an earth terminal, and cross-over connection one filter capacitor between this principal voltage output and this earth terminal, this nothing constraint rectifier with this forward first end of rectifier be connected first end and second end of this secondary power lines circle respectively, this nothing constraint rectifier and this forward second end of rectifier are connected in a tie point, this tie point connects earth terminal, be connected in series an energy storage inductor between first end of this secondary power lines circle and this voltage output end, wherein this rectifier or not have the constraint rectifier be a N channel mos field-effect transistor forward, one P channel mos field-effect transistor, one N passage connects surface field-effect transistor or a P passage connects surface field-effect transistor; And

One signal distributor, comprise one first output, one second output and a common link, wherein this first output and this second output are connected forward control end of rectifier of this nothing constraint rectifier and this respectively, this common connection end is connected in this forward tie point of second end of rectifier and this nothing constraint rectifier, voltage difference by this first output and this second output, the circuit of decision this common connection end of conducting and this first output or this second output, and respectively a voltage signal is distributed to this forward rectifier control end of this nothing constraint rectifier maybe, wherein this signal distributor comprises one first diode and one second diode, the positive pole of this first diode and this second diode is connected to this common connection end, and the negative pole of this first diode and this second diode is respectively this first output and this second output.

2. the forward converter with self-driven synchronous rectifier according to claim 1, first end that it is characterized in that this secondary drive coil and second end are connected first output and second output of this signal distributor respectively, in order to this voltage signal to be provided.

3. the forward converter with self-driven synchronous rectifier according to claim 1, it is characterized in that also comprising a potential displacement device, it comprises a first input end, one second input, one first output and one second output, wherein this first input end and this second input are connected first end and second end of this secondary drive coil respectively, this first output and this second output are connected first output and second output of this signal distributor respectively, make input voltage be exported again by displacement one phase-shifted amount, in order to this voltage signal to be provided, wherein this potential displacement device comprises an electric capacity, one diode and a Zener diode, wherein an end of this electric capacity is as this first input end, the other end of this electric capacity is connected with the positive pole of this diode, its tie point is as this first output, the negative pole of this diode connects the negative pole of this Zener diode, and the anodal while of this Zener diode is as this second input and this second output.

4. the forward converter with self-driven synchronous rectifier according to claim 1, it is characterized in that also comprising subordinate output, this subordinate output comprises a subordinate secondary power lines circle, adjuster after the level, one subordinate power circuit, wherein this subordinate power circuit comprises forward rectifier of a subordinate, one subordinate does not have the constraint rectifier, one subordinate energy storage inductor, one subordinate voltage output end and earth terminal, and cross-over connection one subordinate filter capacitor between this subordinate voltage output end and this earth terminal, this subordinate forward rectifier and this subordinate second end that do not have a constraint rectifier is connected in earth terminal, this subordinate forward first end of rectifier connects second end of this subordinate secondary power lines circle, this subordinate does not have the end that first end that retrains rectifier connects this secondary back adjuster and this subordinate energy storage inductor, the other end of this secondary back adjuster is connected in first end of this second subprime electric power coil, and this secondary back adjuster connects an ON-OFF control circuit, the other end of this subordinate energy storage inductor connects this subordinate voltage output end, this subordinate do not have constraint rectifier and this subordinate forward the control end of rectifier be connected this main power circuit respectively this forward rectifier and this nothing retrain the control end of rectifier, wherein this secondary back adjuster is a suspension control switch, and this ON-OFF control circuit is a driver ic, and this subordinate forward rectifier or do not have the constraint rectifier be a N channel mos field-effect transistor, one P channel mos field-effect transistor, one N passage connects surface field-effect transistor or a P passage connects surface field-effect transistor.

5. the forward converter with self-driven synchronous rectifier according to claim 1, it is characterized in that also comprising subordinate output, this subordinate output comprises a subordinate secondary power lines circle, adjuster after the level, one subordinate power circuit, wherein this subordinate power circuit comprises forward rectifier of a subordinate, one subordinate does not have the constraint rectifier, one subordinate energy storage inductor, one subordinate voltage output end and earth terminal, and cross-over connection one subordinate filter capacitor between this subordinate voltage output end and this earth terminal, this subordinate forward rectifier and this subordinate first end that do not have a constraint rectifier is connected in a tie point, this tie point is connected in series this subordinate energy storage inductor with this subordinate voltage output end, this subordinate forward rectifier does not have second end that second end that retrains rectifier is connected this secondary back adjuster and this subordinate secondary power lines circle respectively with this subordinate, the other end of this secondary back adjuster is connected in first end of this subordinate secondary power lines circle, this secondary back adjuster connects an ON-OFF control circuit, the control end that this subordinate does not have a constraint rectifier connects the control end of the nothing constraint rectifier of this main power circuit, wherein this subordinate rectifier or not have the constraint rectifier be a N channel mos field-effect transistor forward, one P channel mos field-effect transistor, one N passage connects surface field-effect transistor or a P passage connects surface field-effect transistor.

6. the forward converter with self-driven synchronous rectifier according to claim 5, it is characterized in that the forward control end of rectifier this control end of rectifier forward of connecting this main power circuit of this subordinate, and this secondary back adjuster is a suspension control switch, and this ON-OFF control circuit is a driver ic.

7. the forward converter with self-driven synchronous rectifier according to claim 5, it is characterized in that also comprising a subordinate secondary drive coil and an one drive circuit, this drive circuit is connected in the forward control end of rectifier of this subordinate secondary drive coil and this subordinate, and second end of this subordinate secondary drive coil is connected in forward second end of rectifier of this subordinate.

8. the forward converter with self-driven synchronous rectifier according to claim 7 it is characterized in that this secondary back adjuster is a suspension control switch, and this ON-OFF control circuit is a driver ic.

9. the forward converter with self-driven synchronous rectifier according to claim 7 it is characterized in that this secondary back adjuster is a magnetic amplifier, and this ON-OFF control circuit is a reset circuit.

10. the forward converter with self-driven synchronous rectifier according to claim 7, it is characterized in that this drive circuit comprises one first resistance and one second resistance, this first resistance and an end of this second resistance are connected first end and second end of this subordinate secondary drive coil respectively, and the other end of this first resistance and this second resistance is connected to the forward control end of rectifier of this subordinate.

11. the forward converter with self-driven synchronous rectifier according to claim 7, it is characterized in that this drive circuit comprises a diode, one npn bipolar transistor, one PNP bipolar transistor, one first resistance and one second resistance, the emitter of this npn bipolar transistor and this PNP bipolar transistor is connected to the forward control end of rectifier of this subordinate, the base stage of this npn bipolar transistor and this PNP bipolar transistor is connected to a tie point, one end of this first resistance and this second resistance is connected to this tie point, this first resistance and the other end of this second resistance are connected the collector electrode of this npn bipolar transistor and this PNP bipolar transistor respectively, it connects the negative pole of this diode and second end of this subordinate secondary drive coil respectively, and the positive pole of this diode connects first end of this subordinate secondary drive coil.

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