CN105375771B - Phase-shift full-bridge converter control circuit of DC/DC power supply device - Google Patents

Abstract

The present invention relates to a phase-shifted full-bridge converter control circuit of a DC/DC power supply device, comprising a first AND gate and a first OR gate; the first AND gate has two input terminals and an output terminal, the two input terminals are respectively electrically connected to a first and a fourth electronic switch of a phase-shifted full-bridge converter; the first OR gate has a first and a second input terminal and an output terminal, the first input terminal of the first OR gate is electrically connected to the output terminal of the first AND gate, the second input terminal receives a synchronous rectification switch control signal in a continuous conduction mode, the output terminal of the first OR gate is electrically connected to the synchronous rectification switch of the phase-shifted full-bridge converter, the synchronous rectification switch can be controlled to be turned on by the present invention in both the continuous conduction mode and the discontinuous conduction mode, thereby reducing energy loss in the discontinuous conduction mode and increasing conversion efficiency.

Description

Phase shift full bridge converter control circuit for DC/DC power supply unit

technical field

The invention relates to a converter control circuit, in particular to a control circuit for controlling a secondary side switch of a phase-shift full-bridge converter of a DC/DC power supply device.

Background technique

Please refer to FIG. 4 , the conventional phase-shift full-bridge converter 10 has a primary side and a secondary side. The primary side of the phase-shift full-bridge converter 10 has first to fourth electronic switches Q1 - Q4 , a positive input terminal 11 , a negative input terminal 12 and a primary coil 13 . The four electronic switches Q1-Q4 are metal-oxide-semiconductor field-effect transistors (Metal-Oxide-Semiconductor Field-Effect Transistor; MOSFET), and the drains of the first and third electronic switches Q1 and Q3 are electrically connected to the input positive Terminal 11, the sources of the second and fourth electronic switches Q2 and Q4 are electrically connected to the input negative terminal 12, the source of the first electronic switch Q1 and the drain of the second electronic switch Q2 are electrically connected to the primary The first end of the side coil 13 , and the source of the third electronic switch Q3 and the drain of the fourth electronic switch Q4 are both electrically connected to the second end of the primary side coil 13 .

The secondary side of the phase-shift full-bridge converter 10 includes a secondary side coil 14, an output positive terminal 15, an output negative terminal 16, a first synchronous rectification switch Q5, a second synchronous rectification switch Q6 and An output inductor L. The first and second synchronous rectification switches Q5 and Q6 are MOSFETs. The sources of the first and second synchronous rectification switches Q5 and Q6 are electrically connected to the negative output terminal 16, and the drain of the first synchronous rectification switch Q5 is electrically connected to the first end of the secondary coil 14. The drains of the two synchronous rectification switches Q6 are electrically connected to the second terminal of the secondary coil 14 , and the center tap of the secondary coil 14 is connected to the positive output terminal 15 through the output inductor L.

The phase-shift full-bridge converter 10 can be divided into continuous conduction mode (Continue Condition Mode; CCM) and discontinuous conduction mode (Discontinue Condition Mode; DCM) during operation. The continuous conduction mode means that the output current flowing through the output inductor L on the secondary side is continuously positive and not zero, while the discontinuous conduction mode means that the output current flowing through the output inductor L on the secondary side is continuously positive value and a situation equal to zero occurs.

The gates A to D of the first to fourth electronic switches Q1 to Q4 and the gates E and F of the first and second synchronous rectification switches Q5 and Q6 are respectively electrically connected to a control integrated circuit (Integrated Circuit; IC) The first to sixth output pins of 100, the first to sixth output pins of the control integrated circuit 100 respectively output first to sixth control signals to control the first to fourth electronic switches Q1-Q4 and the first 1. Whether the second synchronous rectification switches Q5 and Q6 are turned on or not determines the conversion efficiency of the phase-shift full-bridge converter 10 from the input energy of the primary side to the output of the secondary side. However, the conduction control of the first to fourth electronic switches Q1 - Q4 and the first and second synchronous rectification switches Q5 and Q6 in the existing control integrated circuit 100 is only designed for the continuous conduction mode.

Please refer to FIG. 5 , the first control signal is inverse to the second control signal, the third control signal is inverse to the fourth control signal, and the first control signal leads the third control signal by 90 degrees. In the continuous conduction mode, the output current IL flowing through the inductor L is continuously positive and not zero, so the first and second synchronous rectification switches Q5 and Q6 only need to induce current in the secondary side coil 14 When the direction is opposite to the direction of the output current IL, control the first synchronous rectification switch Q5 or the second synchronous rectification switch Q6 to be non-conductive, so as to prevent the secondary side coil 14 from inducing a reverse induced current, resulting in the The loads of the positive and negative output terminals 15 and 16 are damaged due to reverse current.

For example, please refer to FIG. 6A , in a first case, when only the gates of the first and fourth electronic switches Q1 and Q4 are turned on at high potential, an input current Iin is generated by the primary side coil 13 The first terminal flows in and flows out from its second terminal, and the induced current I _sense induced by the secondary side coil 14 is connected to the first terminal of the secondary side coil 14 and the first synchronous rectification switch Q5 or the secondary The central tap of the side coil 14 flows out. Normally, the load should receive the current flowing out of the positive output terminal 15 to actuate. If the first synchronous rectification switch Q5 is turned on at this time, the induced current I The _sense will reversely flow to the output negative terminal 16 via the first terminal of the secondary measuring coil 14, causing damage to the load. Therefore, in this situation, the gate E of the first synchronous rectification switch Q5 must be at a low potential to maintain a non-conductive state, so that the induced current I _sense will not flow to the output negative terminal 16 after it is generated. , and the central tap of the secondary measuring coil 14 flows through the output inductor L to the positive output terminal 15 to provide the load with a current in the correct direction.

Similarly, please refer to FIG. 6B. In a second case, when only the gates of the second and third electronic switches Q2 and Q4 are turned on at high potential, the input current Iin is supplied by the first coil 13 of the primary side. The two ends flow in and flow out from the first end, and the direction of the induced current I _sense induced by the secondary side flows in from the first end of the secondary side coil 14 or the center tap of the secondary side coil 14, if At this time, the second synchronous rectification switch Q6 is turned on, and the induced current I _sense will flow out from the second terminal connected to the second synchronous rectification switch Q6 of the secondary side coil 14 to the output negative terminal 16, forming an inverse to the current and cause damage to the load. Therefore, in this situation, the gate F of the second synchronous rectification switch Q6 must be at a low potential to maintain a non-conductive state, so that the induced current I _sense cannot flow through the second synchronous rectification switch Q6 to generate Reverse current flows to the negative output terminal 16 . In other situations, both the first and second synchronous rectification switches Q5 and Q6 can be turned on to reduce loss and improve conversion efficiency.

However, the control integrated circuit 100 of the phase-shift full-bridge converter in the prior art only controls the first to fourth electronic switches Q1-Q4 and the first and second synchronous rectification switches Q5 and Q6 when it is in the continuous conduction mode. on/off. In the discontinuous conduction mode, the first and second synchronous rectification switches Q5 and Q6 on the secondary side are directly turned off, and the transfer is achieved only through the parasitic diodes of the first and second synchronous rectification switches Q5 and Q6. The purpose of energy, but only through the parasitic diode to transfer energy will produce more energy loss, resulting in low conversion efficiency. Therefore, it is necessary to further improve the switching control of the phase-shifted full-bridge converter in the prior art in the discontinuous conduction mode.

Contents of the invention

In view of the fact that the control integrated circuit of the existing phase-shift full-bridge converter only controls the continuous conduction mode and does not control the discontinuous conduction mode, resulting in the disadvantage of low conversion efficiency, the purpose of the present invention is to provide a DC The phase-shift full-bridge converter control circuit of the DC power supply device enables the phase-shift full-bridge converter to perform different controls in the continuous conduction mode and the discontinuous conduction mode, so as to achieve the discontinuous conduction mode The purpose of reducing energy loss and improving conversion efficiency in pass mode.

The technical solution of the present invention is to provide a phase-shift full-bridge converter control circuit of a DC/DC power supply device, which cooperates with a control integrated circuit to jointly control a phase-shift full-bridge converter, the phase-shift full-bridge conversion The device includes first to fourth electronic switches connected to a full bridge structure, a first synchronous rectification switch and a second synchronous rectification switch, the control integrated circuit has first to sixth output pins; the DC/DC power supply device The phase-shifted full-bridge converter control circuit includes a first unit and a second unit, wherein:

This first unit contains:

a first AND gate, the two input terminals of which are respectively connected to the first and fourth output pins of the control integrated circuit to receive a first and fourth control signal; and

A first OR gate with:

a first input end connected to the output end of the first AND gate;

a second input terminal receiving a second synchronous rectification switch control signal for controlling a second synchronous rectification switch of the phase-shift full-bridge converter in continuous conduction mode;

an output end connected to the control end of the second synchronous rectification switch of the phase-shift full-bridge converter;

This second unit contains:

a first AND gate, the two input terminals of which are respectively connected to the second and third output pins of the control integrated circuit to receive a second and a third control signal; and

A first OR gate with:

a first input end connected to the output end of the first AND gate of the second unit;

a second input end, receiving a first synchronous rectification switch control signal used to control the phase-shift full-bridge converter in continuous conduction mode;

An output terminal is connected to the control terminal of the first synchronous rectification switch of the phase-shift full-bridge converter.

The control circuit of the phase-shift full-bridge converter uses a logic circuit to realize the second control signal of the secondary side of the phase-shift full-bridge converter according to the control signals of the first to fourth electronic switches on the primary side of the phase-shift full-bridge converter. 1. The conduction control of the second synchronous rectification switch is output by the output terminal of the first OR gate of the first unit of the control circuit in the continuous conduction mode and in the discontinuous conduction mode to control the second synchronous rectification switch. A second synchronous control signal, and a first synchronous signal for controlling the first synchronous rectification switch in the continuous conduction mode and in the discontinuous conduction mode is output from the output terminal of the first OR gate of the second unit of the control circuit control signal.

The control circuit of the phase-shifted full-bridge converter of the present invention can output different control signals in continuous and discontinuous conduction modes, so as to perform the first and second synchronous rectification switches on the secondary side of the phase-shifted full-bridge converter control, so that the phase-shift full-bridge converter can also be controlled in the discontinuous conduction mode to reduce energy loss and increase conversion efficiency. Moreover, the present invention is implemented with logic circuits, and many logic integrated circuits currently on the market include AND gates and OR gates. Therefore, the present invention only needs to set up a logic integrated circuit and simple wiring to realize it, and does not need to additionally set up sophisticated electronic circuits. components or complex wiring structures.

Description of drawings

FIG. 1 is a circuit diagram of a first preferred embodiment of the present invention.

FIG. 2 is a timing diagram of a phase-shifted full-bridge converter in discontinuous conduction mode.

FIG. 3 is a circuit diagram of a second preferred embodiment of the present invention.

FIG. 4 is a circuit diagram of a phase-shifted full-bridge converter in the prior art.

FIG. 5 is a timing diagram of the phase-shifted full-bridge converter in continuous conduction mode.

FIG. 6A is a circuit diagram of the sense current flow of the phase-shift full-bridge converter in a first situation.

FIG. 6B is a circuit diagram of the induced current flow of the phase-shift full-bridge converter in a second situation.

detailed description

The technical means adopted by the present invention to achieve the intended invention purpose are further described below in conjunction with the drawings and preferred embodiments of the present invention.

Please refer to Fig. 1, the phase-shift full-bridge converter control circuit 20 of the DC/DC power supply device of the present invention cooperates with a control integrated circuit 26 to jointly control a phase-shift full-bridge converter 10, the phase-shift full-bridge converter For the device 10, reference may be made to the existing circuit shown in FIG. 4 , and its circuit structure will not be repeated here. The control integrated circuit 26 has first to fourth output pins OUTA-OUTD, and the first to fourth output pins OUTA-OUTD are respectively connected to the first to fourth electronic switches in the phase-shift full-bridge converter 10 The control terminals A to D of Q1 to Q4, and the first to fourth output pins OUTA to OUTD respectively output a first to fourth control signals to control the conduction and switching of the first to fourth electronic switches Q1 to Q4 no.

The phase-shift full-bridge converter control circuit 20 includes a first unit 20a and a second unit 20b.

The first preferred embodiment of the first unit 20a includes a first AND gate 21a, a first OR gate 22a, a second OR gate 23a, a current detection circuit 24 and a second AND gate 25a.

The first AND gate 21a and the second OR gate 23a respectively have two input terminals and an output terminal. The two input terminals of the first AND gate 21a are respectively electrically connected to the first and fourth output pins OUTA and OUTD of the control integrated circuit 26, and the two input terminals of the second OR gate 23a are also electrically connected to the The first and fourth output pins OUTA and OUTD of the integrated circuit 26 are controlled to receive the first and fourth control signals. The first OR gate 22a and the second AND gate 25a respectively have a first input terminal, a second input terminal and an output terminal. The first input terminal of the first OR gate 22a is electrically connected to the output terminal of the first AND gate 21a, and the second input terminal of the first OR gate 22a receives a signal used to control the phase-shift mode in continuous conduction mode. The second synchronous rectification switch control signal S1a of whether the second synchronous rectification switch Q6 of the full-bridge converter 10 is on or not, and the output terminal of the first OR gate 22a is electrically connected to the control terminal F of the second synchronous rectification switch Q6 , to output a second synchronous control signal S2a for controlling whether the second synchronous rectification switch Q6 is turned on or not.

The current detection circuit 24 is used to detect the input or output current of the primary side or the secondary side, and output a high potential signal in the continuous conduction mode, and output a low potential signal in the discontinuous conduction mode. The first input end of the second AND gate 25a is electrically connected to the output end of the second OR gate 23a, and the second input end of the second AND gate 25a is electrically connected to the current detection circuit 24 to receive the current detection circuit 24 output signal, and the output terminal of the second AND gate 25a is electrically connected to the control terminal F of the second synchronous rectification switch Q6 to output in the continuous conduction mode to control the conduction and connection of the second synchronous rectification switch Q6 No second synchronous rectification switch control signal S1a.

Similarly, a first synchronous control signal S2b of the control terminal E of the second synchronous rectification switch Q5 of the phase-shift full-bridge converter 10 is generated by the second unit 20b, and the second unit 20b includes a first AND gate 21b , a first OR gate 22b, a second OR gate 23b and a second AND gate 25b. The first AND gate 21b and the second OR gate 23b respectively have two input terminals and an output terminal. Two input terminals of the first AND gate 21b and the second OR gate 23b of the second unit 20b are respectively electrically connected to the second and third output pins OUTB and OUTC of the control integrated circuit 26 . The first OR gate 22b and the second AND gate 25b respectively have a first input terminal, a second input terminal and an output terminal. The first input end of the second AND gate 25b is electrically connected to the output end of the second OR gate 23b, and its second input end is electrically connected to the current detection circuit 24 to receive the signal output by the current detection circuit 24, and the The output terminal of the second AND gate 25b outputs a first synchronous rectification switch control signal S1b for controlling the first synchronous rectification switch Q5 of the phase-shift full-bridge converter 10 in the continuous conduction mode. The first input end of the first OR gate 22b is electrically connected to the output end of the first AND gate 21b, and the second input end of the first OR gate 22b is electrically connected to the output end of the second AND gate 25b, so as to Receive the first synchronous rectification switch control signal S1b, and the output terminal of the first OR gate 22b is electrically connected to the control terminal E of the first synchronous rectification switch Q5 to output a signal for controlling the first synchronous rectification switch Q5 A first synchronous control signal S2b is used to control whether the first synchronous rectification switch Q5 is turned on or not.

Please refer to FIG. 2 , which is the first to fourth control signals, the A timing diagram of the output current IL of the inductor L and the control signals of the first and second synchronous rectification switches Q5 and Q6 at the control terminals E and F of the first and second synchronous rectification switches Q5 and Q6 . The first control signal is inverse to the second control signal, the third control signal is inverse to the fourth control signal, and the first control signal leads the third control signal by 90 degrees. In the discontinuous conduction mode, the first and second synchronous rectification switches Q5 and Q6 are only turned on when the corresponding first to fourth electronic switches Q to Q4 of the phase-shift full-bridge converter 10 are turned on to transfer energy. , it is turned on to reduce energy loss and increase conversion efficiency.

For example, as shown in FIG. 6A, when the first and fourth electronic switches Q1 and Q4 are turned on, the induced current I _sense flows out from the central tap of the secondary side coil 14, and the second synchronous rectification switch Q6 is only turned on under this condition, so that the induced current I _sense flows out from the center tap of the secondary side coil 14, flows through the output inductor L, and then flows to a terminal 15 electrically connected to the output positive and negative terminals. , 16, then flows through the sixth electronic switch Q6 from the negative output terminal 16, and then flows to the second end of the secondary side coil 14, and in other periods, the second synchronous rectification switch Q6 is It is non-conductive to protect the load from generating reverse current when the output inductor L current IL is zero, causing the load to be damaged.

Similarly, as shown in FIG. 6B, when the second and third electronic switches Q2 and Q3 are turned on, the induced current I _sense flows in from the second end of the secondary side coil 14, and the first synchronous rectification switch Q5 It is only turned on under this condition, so that the induced current I _sense flows out from the central tap of the secondary coil 14, flows through the output inductance L, and then flows to a circuit that is electrically connected to the output positive and negative terminals 15 and 16. The load between them flows through the first synchronous rectification switch Q5 from the output negative terminal 16, and then flows to the first end of the secondary side coil 14, and in other periods, the first synchronous rectification switch Q5 does not conduct To protect the load when the current IL of the output inductor L is zero, no reverse current will be generated and the load will be damaged.

Judging by the timing diagram in Figure 2, the following truth table can be summarized:

A B C D. E. f 0 1 1 0 1 0 0 1 0 1 0 0 1 0 0 1 0 1 1 0 1 0 0 0 0 1 1 0 1 0 0 1 0 1 0 0 1 0 0 1 0 1 1 0 1 0 0 0

From the above truth table, it can be deduced that the control terminals E and F of the fifth and sixth electronic switches Q5 and Q6 and the control terminals A to D of the first to fourth electronic switches Q1 to Q4 are in discontinuous conduction mode. Logic:

Further referring to the timing diagram of FIG. 6 , the truth table of the fifth and sixth electronic switches Q5 and Q6 of the phase-shift full-bridge converter 10 in the continuous conduction mode can be summarized as follows:

The logic of the control terminals E and F of the fifth and sixth electronic switches Q5 and Q6 and the control terminals A to D of the first to fourth electronic switches Q1 to Q4 in the continuous conduction mode is deduced from the above truth table relation:

According to the above-mentioned discontinuous conduction mode and continuous conduction mode, the logic relationship between the control terminals E and F of the fifth and sixth electronic switches Q5 and Q6 can be designed to control the phase-shift full-bridge converter 10 of the present invention. Circuit 20.

Further, please refer to FIG. 3 , the phase-shift full-bridge converter control circuit 20 according to the second preferred embodiment of the present invention includes the first unit 20a and the second unit 20b. The first unit 20a has the first AND gate 21a and the first OR gate 22a. The control integrated circuit 26 has the function of outputting the first and second synchronous rectification switch control signals of the first and second synchronous rectification switches Q5 and Q6 in continuous conduction mode, that is, the control integrated circuit 26 further has a fifth , the sixth output pins OUTE, OUTF. In this preferred embodiment, the integrated circuit number of the control integrated circuit 26 is UCC28950. The two input terminals of the first AND gate 21a are respectively electrically connected to the first and fourth output pins OUTA and OUTD of the integrated circuit 26, and the first input terminal of the first OR gate 22a is electrically connected to the first and The output terminal of gate 21a. And the sixth output pin OUTF of the control integrated circuit is electrically connected to the second input end of the first OR gate 22a to output the first phase-shift full-bridge converter 10 for controlling the phase-shift full-bridge converter 10 in the continuous conduction mode. The second synchronous rectification switch control signal S1a indicating whether the second synchronous rectification switch Q6 is on or not is sent to the second input terminal of the first OR gate 22a. The output end of the first OR gate 22a is electrically connected to the control end F of the second synchronous rectification switch Q6 to output the second synchronous control signal S2a to control whether the second synchronous rectification switch Q6 is turned on or not.

Similarly, the first synchronous control signal received by the control terminal E of the first synchronous rectification switch Q5 on the secondary side of the phase-shift full-bridge converter 10 is generated by the second unit 20b of the phase-shift full-bridge converter control circuit 20 . The second unit 20b has the first AND gate 21b and the first OR gate 22b, and the two input terminals of the first AND gate 21b are electrically connected to the second and third output pins OUTB of the control integrated circuit 26 respectively. , OUTC, the first input end of the first OR gate 22b is electrically connected to the output end of the first AND gate 21b, and the second input end of the first OR gate 22b is electrically connected to the fifth of the control integrated circuit 26 The output pin OUTE is used to receive the first synchronous rectification switch control signal S1b for controlling whether the first synchronous rectification switch Q5 of the phase-shift full-bridge converter 10 is on or not in the continuous conduction mode. The output end of the first OR gate 22 is electrically connected to the control end E of the first synchronous rectification switch Q5 to output the second synchronous control signal S2b to control whether the first synchronous rectification switch Q5 is turned on or not.

When the number of logic gates used in the control circuit 20 is more, the control signal may cause a time delay in the process of transmission and logic judgment, so that the signal output by the control integrated circuit 26 cannot be immediately reflected to the control circuit. 20 to control the first and second synchronous rectification switches Q5 and Q6 accurately and without delay, so that reverse current is generated in discontinuous conduction mode and the load is damaged. Therefore, in the first and second preferred embodiments of the present invention, a delay circuit 27 can be further provided, and the delay circuit 27 is electrically connected to the first to fourth output pins OUTA-OUTD of the control integrated circuit 26 and the phase Between the control terminals A-D of the first to fourth electronic switches Q1-Q4 of the shifted full-bridge converter 10 . The two input terminals of the first AND gate 21a of the first unit 20a of the phase-shift full-bridge converter control circuit 20 are directly electrically connected to the first and fourth output pins OUTA and OUTD of the control integrated circuit 26 The two input terminals of the first AND gate 21b of the second unit 20b are directly electrically connected to the second and third output pins OUTB and OUTC of the control integrated circuit 26 . Therefore, the control integrated circuit 26 can delay control of the first to fourth electronic switches Q1 to Q4 of the phase-shift full-bridge converter 10, and control the first to fourth electronic switches at the same time after waiting for the logic judgment of the control circuit 20. Electronic switches Q1-Q4 and the first and second synchronous rectification switches Q5 and Q6. In this preferred embodiment, the delay circuit 27 is a resistor-capacitor delay circuit (RC delay circuit).

The first preferred embodiment of the present invention only utilizes the control signals of the control terminals A to D of the first to fourth electronic switches Q1 to Q4 on the primary side output by the integrated circuit 26 to realize continuous conduction mode and discontinuous conduction mode. In the conduction mode, both the first and second synchronous rectification switches Q5 and Q6 can be controlled. And the second preferred embodiment of the present invention integrates the function of controlling the first and second synchronous rectification switches Q5 and Q6 built in the control integrated circuit 26 in the continuous conduction mode, so as to further reduce the load in the control circuit 20 The number of logic gates makes the logic circuit of the present invention more compact. If the control integrated circuit does not have the built-in function of controlling the first and second synchronous rectification switches Q5 and Q6 in the continuous conduction mode, the first preferred embodiment of the present invention must be used to realize the continuous conduction mode. The functions of the first and second synchronous rectification switches Q5 and Q6 can be controlled in both conduction mode and discontinuous conduction mode. Therefore, the present invention can also control the synchronous rectification switch in the discontinuous conduction mode, so as to reduce energy loss and increase conversion efficiency. And the present invention only utilizes simple logic gate to realize, for this reason, only need to set up a logic integrated circuit with a plurality of logic gates and simple wiring and can realize, need not additionally set complicated and precise electronic element or microprocessor, namely The intended purpose of the present invention can be achieved.

The above descriptions are only preferred embodiments of the present invention, and do not limit the present invention in any form. Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this professional technology Personnel, without departing from the scope of the technical solution of the present invention, when the technical content disclosed above can be used to make some changes or modifications to equivalent embodiments with equivalent changes, but all the content that does not depart from the technical solution of the present invention, according to the present invention Any simple modifications, equivalent changes and modifications made to the above embodiments by the technical essence still belong to the scope of the technical solutions of the present invention.

Claims (7)

1. a kind of phase-shift type full-bridge converters control circuit of DC-DC supply unit, it is total to unification domination set into circuit With being used to controlling a phase-shift type full-bridge converters, the phase-shift type full-bridge converters, which include, connects into the first of full bridge structure to the Four electronic switches, one first synchronous rectification switch and one second synchronous rectification switch, the control integrated circuit have first to the Six output connecting pins, it is characterised in that the phase-shift type full-bridge converters control circuit of the DC-DC supply unit includes one Unit one and a second unit, wherein：

The first module includes：

One first and door, secondly individual input is respectively for being connected to first and the 4th output connecting pin of the control integrated circuit, with The control signal of reception first and the 4th；And

One first OR gate, has：

One first input end, be connected to this first with the output end of door；

One second input, it is received under continuous conduction mode to control the one second of second synchronous rectification switch synchronization whole Flow switch controlling signal；

One output end, it is connected to the control terminal of second synchronous rectification switch；

The second unit includes：

One first and door, secondly individual input is respectively for being connected to second and third output connecting pin of the control integrated circuit, with Receive one second and one the 3rd control signal；And

One first OR gate, has：

One first input end, it is connected to the first of the second unit and the output end of door；

One second input, it is received under continuous conduction mode to control the one first of first synchronous rectification switch synchronization whole Flow switch controlling signal；

One output end, it is connected to the control terminal of first synchronous rectification switch.

2. the phase-shift type full-bridge converters control circuit of DC-DC supply unit according to claim 1, its feature exist In, a current detection circuit is further includeed, to judge when continuous conduction mode, exports a high potential signal, and sentence Break when discontinuous conduction mode, export a low-potential signal, wherein：

The first module further includes：

One second OR gate, secondly individual input is respectively for being connected to first and the 4th output connecting pin of the control integrated circuit, with Receive the one first and the 4th control signal；And

One second and door, have：

One first input end, it is connected to the current detection circuit；

One second input, it is connected to the output end of the second OR gate of the first module；

One output end, the second input of the first OR gate of the first module is connected to, should be under continuous conduction mode with output To control one second synchronous rectification switch control signal of second synchronous rectification switch；

The second unit further includes：

One second OR gate, secondly individual input supplies to be connected to second and third output connecting pin of the control integrated circuit respectively；

One second and door, have：

One first input end, it is connected to the current detection circuit；

One second input, it is connected to the output end of the second OR gate of the second unit；

One output end, the second input of the first OR gate of the second unit is connected to, should be under continuous conduction mode with output To control one first synchronous rectification switch control signal of first synchronous rectification switch.

3. the phase-shift type full-bridge converters control circuit of DC-DC supply unit according to claim 1, its feature exist In, wherein：

Second input of the first OR gate of the first module is electrically connected to the 6th output connecting pin of the control integrated circuit, to connect This is received under continuous conduction mode to control the second synchronous rectification switch control signal of second synchronous rectification switch；And

Second input of the first OR gate of the second unit is electrically connected to the 5th output connecting pin of the control integrated circuit, to connect This is received under continuous conduction mode to control the first synchronous rectification switch control signal of first synchronous rectification switch.

4. the phase-shift type full-bridge converters control electricity of DC-DC supply unit according to any one of claim 1 to 3 Road, it is characterised in that further include：

One delay circuit, electrically connect first to fourth output connecting pin and first to fourth electronic switch of the control integrated circuit Between.

5. the phase-shift type full-bridge converters control circuit of DC-DC supply unit according to claim 4, its feature exist In the delay circuit is a Resistance-Capacitance delay circuit.

6. the phase-shift type full-bridge converters control electricity of DC-DC supply unit according to any one of claim 1 to 3 Road, it is characterised in that wherein：

First to fourth output connecting pin of the control integrated circuit exports first to fourth control signal respectively；

First control signal and second control signal are anti-phase；

3rd control signal and the 4th control signal are anti-phase；And

Leading 3rd control signal of first control signal.

7. the phase-shift type full-bridge converters control circuit of DC-DC supply unit according to claim 6, its feature exist In leading 90 degree of 3rd control signal of first control signal.