WO2017000474A1

WO2017000474A1 - Pre-bias on-and-off circuit, and circuit and method for pre-biasing multi-cascade converter

Info

Publication number: WO2017000474A1
Application number: PCT/CN2015/094601
Authority: WO
Inventors: 郭忠银; 吴乔
Original assignee: 中兴通讯股份有限公司
Priority date: 2015-07-01
Filing date: 2015-11-13
Publication date: 2017-01-05
Also published as: CN106329905A

Abstract

A pre-bias on-and-off circuit, and a circuit and a method for pre-biasing a multi-cascade converter. The pre-bias on-and-off circuit (500) comprises a detection module and a control module. The detection module is connected to an output terminal of the multi-cascade converter and is set to detect an output signal of the multi-cascade converter. The control module is connected to a pull-push circuit (200) of the multi-cascade converter and is set to generate a pre-bias signal when the output signal is a pre-set output signal according to the detected output signal, and controls a rectifier tube of the pull-push circuit to drive the on-and-off circuit by utilizing the pre-bias signal. The pre-bias on-and-off circuit determines whether there is a need to perform pre-biasing to switch on and off by detecting the output signal of the multi-cascade converter, which can be easily realized and the entry point control is precise, so that the problem of a device being damaged due to an excessive inverse current of a freewheel switching tube caused by the pre-bias voltage of a load is solved, and the output voltage collapse of the converter is also prevented.

Description

Pre-biasing switch circuit and multi-cascade converter pre-bias circuit and method

Technical field

The present invention relates to the field of communications, and in particular, to a pre-biasing switch circuit and a multi-cascade converter pre-bias circuit and method.

Background technique

Please refer to FIG. 1 , which is a converter circuit composed of a buck conversion circuit (BUCK circuit) and a push-pull circuit two-stage topology circuit, an output filter circuit, a PWM control circuit and a fixed duty output circuit.

The BUCK circuit includes a rectifier switch transistor QR, a freewheeling switch tube QF, a first inductor Lout1, and a first capacitor Co1; the primary side of the push-pull circuit includes two main tubes VT3 and VT4, and the secondary side includes two rectifier tubes VT5 and VT6; The output filter circuit comprises a second output capacitor Co2, a second inductor Lout2 and a third capacitor filter circuit Co3; a pulse width modulation (Pulse Width Modulation, PWM for short) control circuit and a fixed duty cycle output circuit, respectively, a PWM circuit control BUCK The drive of the circuit, the fixed duty cycle output circuit controls the two metal-oxide-semiconductor field effect transistors (MOS) driven by the push-pull circuit.

When the machine is turned on and off, the duty cycle of the drive signal in the push-pull process of the push-pull circuit is about 50% fixed duty cycle. At the time of power-on, the duty cycle of the drive signal of the rectifier switch QR starts to be low, and then gradually increases, and the duty ratio of the drive signal of the freewheeling switch QF starts to be high, and then gradually decreases. If there is voltage in the load, the capacitor Co3 forms a loop through the push-pull circuit, the inductor L and the freewheeling switch tube QF, and generates a backflow current.

When the power is turned off, the first inductor, the first capacitor, and the second capacitor also generate a backflow current, which is poured back to the input end. In practical applications, especially when the power is turned on and off under the condition of large capacitance and no load, the reverse current will be larger. Therefore, when the voltage is present in the load, the following effects will be affected on the DC converter circuit: on the one hand, the output waveform of the DC converter is not monotonous, and there is a risk of falling; on the other hand, the flow through the freewheeling switch tube The reverse current is very large. When the rated value is exceeded, the freewheeling switch tube and the load will be damaged, and the leakage source stress of the secondary side switching tube of the push-pull circuit will also exceed the standard.

At present, there are two common methods for solving the above problems: the first type detects the current of the freewheeling switch tube when the power is turned on, and when the reverse current of the freewheeling switch tube is determined to be zero, the freewheeling switch tube is driven to open, and the detection continues The reverse current of the current switch tube is very complicated and is not used. The second method is to detect the soft start (referred to as SS) signal in the primary side PWM control chip. When the SS signal reaches the set value, the push is turned on. The secondary side of the pull circuit is driven. However, as the input voltage and load conditions of the module are different, the timing of this switching point is not the same. It is difficult to track this switching point in control. If the premature switching cannot avoid the problem of backflow, the too late switching will make the module in the Schottky rectification state for a long time.

Summary of the invention

The main technical problem to be solved by the embodiments of the present invention is to provide a pre-biasing switch circuit and a multi-cascade converter pre-bias circuit and method, which solve the complicated control of the existing DC converter and easily damage the circuit device and switch Not easy to control The problem of defects.

To solve the above problem, an embodiment of the present invention provides a pre-biasing switch circuit, including a detecting module and a control module:

The detecting module is connected to an output end of the multi-cascade converter and configured to detect an output signal of the multi-cascade converter;

The control module is connected to the push-pull circuit of the multi-cascade converter, and is configured to generate a pre-bias signal according to the detected output signal, when the output signal is a preset output signal, and utilize the pre-bias The signal controls the rectifier of the push-pull circuit to drive the switching circuit.

In an embodiment of the invention, the push-pull circuit includes a secondary rectifier driving; the rectifier driving the switching circuit of the push-pull circuit by using the pre-bias signal includes: utilizing the pre-bias The signal is controlled to control the secondary rectifier of the push-pull circuit to drive the switching circuit.

In one embodiment of the invention, the output signal comprises an output sensor SENSE signal or an output VOUT signal.

In an embodiment of the invention, the preset output signal comprises: a preset on output signal or a preset off output signal.

In order to solve the above problems, an embodiment of the present invention further provides a multi-cascade converter pre-biasing circuit, which includes a multi-cassette converter and a pre-biasing switch circuit as described in any of the above;

a detection module of the pre-biasing switcher circuit is coupled to an output of the multi-cascade converter, and configured to detect an output signal of the multi-cascade converter;

The pre-biasing switch circuit is connected to the push-pull circuit of the multi-cascade converter, and is configured to generate a pre-bias signal when the output signal is a preset output signal according to the detected output signal, and utilize The pre-bias signal controls a rectifier drive circuit of the push-pull circuit.

In one embodiment of the invention, the multi-cascade converter is a converter of isolated or non-isolated topology.

In an embodiment of the invention, the multi-cascade converter is a cascade converter or a multi-cascade converter.

In one embodiment of the invention, the multi-cascade converter is a variable duty cycle converter.

To solve the above problem, an embodiment of the present invention further provides a multi-cascade converter pre-biasing method, including:

Detecting an output signal of the multi-cascade converter;

Generating a pre-bias signal when the output signal is a preset output signal;

The rectifier-driven switching circuit of the push-pull circuit in the multi-cascade converter is controlled by the pre-bias signal.

The beneficial effects of the embodiments of the present invention are:

The pre-biasing switch circuit and the multi-cascade converter pre-bias circuit and method provided by the embodiment of the invention comprise a detection module and a control module: the detection module is connected to the output end of the multi-cascade converter And being configured to detect an output signal of the multi-cascade converter; the control module is connected to the push-pull circuit of the multi-cascade converter, and is configured to generate a pre-bias signal according to the detected output signal, when the output signal is a preset output signal, The pre-bias signal is used to control the rectifier driving circuit of the push-pull circuit. Compared with the prior art, the embodiment of the present invention adds a pre-biasing switch circuit to the DC converter, and detects whether the pre-bias switch is required by detecting the output signal of the multi-cassette converter, which is simple to implement, and the entry point is simple. Control is precise. The problem that the reverse current of the freewheeling switch tube is excessively damaged due to the load pre-bias voltage is solved, and the drop of the output voltage of the converter is also prevented.

DRAWINGS

1 is a schematic structural view of a conventional multi-cascade converter;

2 is a schematic structural diagram of a pre-bias circuit of a multi-cascade converter according to Embodiment 1 of the present invention;

3 is a schematic structural diagram of a multi-stage converter formed by a BUCK circuit and a push-pull circuit in a pre-bias circuit of a multi-cascade converter according to Embodiment 1 of the present invention;

4 is a schematic structural diagram of a circuit of a pre-biasing switch machine according to Embodiment 2 of the present invention;

5 is a schematic structural diagram of a circuit of a pre-biasing switch machine according to Embodiment 3 of the present invention;

FIG. 6 is a flowchart of a method for pre-biasing a multi-cascade converter according to Embodiment 4 of the present invention.

detailed description

The technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. It is a partial embodiment of the invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

Embodiment 1:

The embodiment provides a structure of a pre-biasing circuit of a multi-cascade converter. As shown in FIG. 2, in the embodiment, a multi-cascade converter is taken as an example for description. The bias circuit includes a BUCK circuit 100, a push-pull circuit 200, an output filter circuit 300, a PWM control circuit and a fixed duty cycle output circuit 400, and a pre-bias switcher circuit 500. One end of the pre-biasing switch circuit 500 is connected to the output end of the output filter circuit 300, and the other end is connected to the push-pull circuit 200. The BUCK circuit 100 adopts synchronous rectification technology, and the secondary side rectification of the push-pull circuit 200 also adopts synchronous rectification technology. As shown in FIG. 3, the BUCK circuit 100 includes a rectifier switch QR, a freewheeling switch QF, and a first inductor Lout1, and outputs a first capacitor Co1. The primary side of the push-pull circuit 200 includes two main controllers VT3 and VT4, and the secondary side includes Two rectifiers VT5, VT6; the output filter circuit 300 includes a second output capacitor Co2, a second inductor Lout2 and a third capacitor filter circuit Co3; a PWM control circuit and a fixed duty output circuit 400, respectively, a PWM circuit control BUCK circuit 100 drive, The fixed duty cycle output circuit controls the two MOS transistors of the primary side of the push-pull circuit 200. The PWM control circuit and the fixed duty output circuit 400, wherein the PWM control circuit controls the driving of the BUCK circuit, and the duty ratio of the fixed duty output circuit is about 50%, which is not equal to 50%. The pre-biasing switch circuit 500 detects the output voltage signal and accurately finds the entry point of the secondary side of the push-pull circuit into the synchronous rectification.

Optionally, the pre-bias signal is generated when the output signal is the preset output signal, and the rectifier driving circuit of the push-pull circuit is controlled by the pre-bias signal. The duty cycle of the BUCK circuit 100 may be after the module is powered on. When the output voltage of the BUCK circuit 100 is turned on by the fixed duty ratio of the push-pull circuit 200, the output voltage reaches the set value. When the pre-bias switcher circuit 500 turns on the push-pull secondary rectifier, the BUCK circuit 100 has entered the synchronous rectification state, and the output voltage does not drop. That is, when the power is turned on, the pre-biasing switch circuit 500 detects that the output voltage does not reach the set value of the output voltage, and causes the push-pull circuit to turn off the rectifier driving of the secondary side to prevent energy backflow. On the contrary, the drive of the secondary side of the push-pull circuit is started. When the output voltage is detected to be lower than the set value by a certain value during shutdown, the secondary side drive signal of the push-pull circuit is turned off to prevent the energy of the load end from being reversed. Here, an optional embodiment in which the output voltage does not reach the output voltage at the time of power-on is a set value preset to turn on the output signal; when the power is turned off, the output voltage is lower than the set value, and the value is a preset closed output signal. An alternative embodiment.

The pre-biasing switcher circuit 500 in this embodiment samples an output signal, optionally connected to the output of the multi-cascade converter through a detection module of the pre-biasing switcher circuit 500, and detects the multi-cascade converter. output signal. It can accurately find the cut-in point of the secondary side rectifier of the push-pull circuit from the body diode to the MOS synchronous rectification, and is not affected by the input voltage, output current and other factors, and shortens the body diode conduction time to a minimum.

It should be noted that the present embodiment only takes the detection of the output voltage signal as an example, and may also be an output signal such as a current signal, which should be understood as long as the signal of the current current in the multi-cascade converter can be accurately determined. can. Similarly, the multi-cassette converter in this embodiment takes a multi-cascade converter as an example, and may also be a converter of a cascade converter, an isolated or non-isolated topology, and a variable duty cycle converter.

The pre-biasing booting circuit of the present embodiment and the DC converter using the same have the following beneficial effects: adding a pre-biasing switching machine circuit to the DC converter, and determining whether it is necessary by detecting whether the output voltage reaches a set value when the power is turned on. Pre-biased power-on, its implementation is simple, and the point-in point control is accurate. The problem that the reverse current of the freewheeling switch tube is excessively damaged due to the load pre-bias voltage is solved, and the drop of the output voltage of the converter is also prevented, and the body diode conduction time of the rectifier MOS tube is minimized.

Embodiment 2:

This embodiment provides a pre-biasing switch circuit, as shown in FIG. 4, when the pre-bias detection circuit detects that the output sensor (SENSE) voltage has reached the set value. The comparator D2 drives the chip enable by comparing the circuit output high level. The characteristic of the D2 driver chip is that the pin INA and pin INB input signals can be transmitted to the pin OUTA and the pin OUTB only when the enable (EN) signal is high. When the pre-bias detection circuit detects that the output voltage has reached the set value, the drive signals of the pin INA and the pin INB are sent to the pin OUTA and the pin OUTB. Thereby, the secondary side rectification MOS tube is driven to achieve the purpose of preventing backflow. When the pin D1A outputs a high level, the pin 3 of the pin D1A is raised by the pin R11. To eliminate the purpose of disturbance. When the output voltage drops to a certain set value, the pin D1A outputs a low level, the pin D2 drives the chip to stop working, and the secondary side rectified MOS tube drive is turned off, thereby preventing backfilling. It is worth noting that in order to perform more accurate control, the present embodiment is optionally applied to a scenario where the output is loaded and the load is closer to the output port.

Embodiment 3:

This embodiment provides a pre-biasing switch circuit, as shown in FIG. 5, when the pre-bias detection circuit detects that the output voltage of the pin VOUT has reached the set value. The comparator D2 drives the chip enable by comparing the circuit output high level. The characteristic of the pin D2 driver chip is that the pin INA and pin INB input signals can be transmitted to the pin OUTA and the pin OUTB only when the EN signal is high. When the pre-bias detection circuit detects that the output voltage has reached the set value, the drive signals of the pin INA and the pin INB are sent to the pin OUTA and the pin OUTB. Thereby, the secondary side rectification MOS tube is driven to achieve the purpose of preventing backflow. When the pin D1A outputs a high level, the pin 3 of the pin D1A is raised by the pin R11 to eliminate the disturbance. When the output voltage drops to a certain set value, the pin D1A outputs a low level, the pin D2 drives the chip to stop working, and the secondary side rectified MOS tube drive is turned off, thereby preventing backfilling. It is worth noting that in order to perform more accurate control, the present embodiment is optionally applied to a scenario where the output is loaded and the load is far from the output port.

Embodiment 4:

A fourth embodiment of the present application provides a multi-cascade converter pre-biasing method. As shown in FIG. 6, the method includes:

S401: detecting an output signal of the multi-cascade converter;

Optionally, the detection module of the pre-biasing switch circuit can detect the output signal of the multi-cascade converter.

S402: generate a pre-bias signal when the output signal is a preset output signal;

The preset output signal includes: a preset on output signal or a preset off output signal. The pre-bias signal is generated when the detection module detects that the output signal of the cascade converter is a preset on output signal or a preset off output signal, and is transmitted through the output stage converter circuit.

S403: Control a rectifier driving switch circuit of the push-pull circuit in the multi-cassette converter by using a pre-bias signal.

It should be noted that the pre-biasing switch circuit needs to be a multi-cascade converter as a variable duty ratio converter, and the output multi-cassette converter is a pre-bias formed by a converter with a fixed duty ratio and an output filter inductor. Circuit. By sampling the output signal of the output filter inductor, the entry point of the secondary rectifier of the push-pull circuit from the body diode to the synchronous rectification of the MOS can be accurately found, and the body diode conduction time is not affected by factors such as input voltage and output current. Shorten to a minimum.

Industrial Applicability: As can be seen from the above description, the detection module of the present invention is connected to the output end of the multi-cascade converter, and is configured to detect an output signal of the multi-cascade converter; the control module is connected to the push-pull circuit of the multi-cascade converter, It is set to generate a pre-bias signal according to the detected output signal, when the output signal is a preset output signal, and control the rectifier driving circuit of the push-pull circuit by using the pre-bias signal. Compared with the prior art, the invention adds pre-bias switch electromechanical to the DC converter The road detects the output signal of the multi-cassette converter to determine whether a pre-biasing switch is required, which is simple to implement and accurate in point-cutting control. The problem that the reverse current of the freewheeling switch tube is excessively damaged due to the load pre-bias voltage is solved, and the drop of the output voltage of the converter is also prevented.

One of ordinary skill in the art will appreciate that all or a portion of the above steps may be accomplished by a program that instructs the associated hardware, such as a read-only memory, a magnetic disk, or an optical disk. Alternatively, all or part of the steps of the above embodiments may also be implemented using one or more integrated circuits. Correspondingly, each module/unit in the foregoing embodiment may be implemented in the form of hardware or in the form of a software function module. The invention is not limited to any specific form of combination of hardware and software.

The above embodiments are only intended to illustrate the technical solutions of the present invention and are not to be construed as limiting the invention. It should be understood by those skilled in the art that the present invention may be modified or equivalently substituted without departing from the spirit and scope of the invention.

Claims

A pre-biasing switch circuit includes a detection module and a control module:

The detecting module is connected to an output end of the multi-cascade converter and configured to detect an output signal of the multi-cascade converter;

The control module is connected to the push-pull circuit of the multi-cascade converter, and is configured to generate a pre-bias signal according to the detected output signal, when the output signal is a preset output signal, and utilize the pre-bias The signal controls the rectifier of the push-pull circuit to drive the switching circuit.
The pre-biasing switcher circuit of claim 1 wherein said push-pull circuit comprises a secondary rectifier drive; said rectifier drive switch circuit for controlling said push-pull circuit using said pre-bias signal comprises : controlling the secondary side rectifier driving switch circuit of the push-pull circuit by using the pre-bias signal.
The pre-biasing switcher circuit of claim 1 wherein said output signal comprises an output sensor SENSE signal or an output VOUT signal.
The pre-biasing switcher circuit according to any one of claims 1 to 3, wherein the preset output signal comprises: a preset on output signal or a preset off output signal.
A multi-cascade converter pre-biasing circuit comprising a multi-cassette converter and a pre-biasing switcher circuit according to any one of claims 1 to 4;

a detection module of the pre-biasing switcher circuit is coupled to an output of the multi-cascade converter, and configured to detect an output signal of the multi-cascade converter;

The pre-biasing switch circuit is connected to the push-pull circuit of the multi-cascade converter, and is configured to generate a pre-bias signal when the output signal is a preset output signal according to the detected output signal, and utilize The pre-bias signal controls a rectifier drive circuit of the push-pull circuit.
The multi-cascade converter pre-biasing circuit of claim 5 wherein said multi-cascade converter is a converter of isolated or non-isolated topology.
A multi-cascade converter pre-biasing circuit according to claim 5, wherein said multi-cascade converter is a cascade converter or a multi-cascade converter.
The multi-cascade converter pre-biasing circuit of claim 5 wherein said multi-cascade converter is a variable duty cycle converter.
A multi-cascade converter pre-biasing method comprising:

Detecting an output signal of the multi-cascade converter;

Generating a pre-bias signal when the output signal is a preset output signal;

The rectifier-driven switching circuit of the push-pull circuit in the multi-cascade converter is controlled by the pre-bias signal.
The multi-cascade converter pre-biasing method according to claim 9, wherein the preset output signal comprises: a preset on output signal or a preset off output signal.