KR102093236B1 - Converter for micro-hybrid converter for preventing reverse current on initial start-up and Method thereof - Google Patents

Abstract

The present invention relates to a converter for a micro-hybrid, and more particularly, to a converter for a micro-hybrid that prevents inflow of current and control instability when the vehicle is initially started.
According to the present invention, even when the synchronous rectification method is applied, it is possible to implement a converter for a micro-hybrid that is more stable in control that does not generate a reverse current phenomenon during initial startup.

Description

{Converter for micro-hybrid converter for preventing reverse current on initial start-up and Method thereof}

The present invention relates to a converter for a micro-hybrid, and more particularly, to a converter for a micro-hybrid that prevents inflow of current and control instability when the vehicle is initially started.

In addition, the present invention relates to a method for preventing reverse current inflow and control instability when the vehicle is initially started.

The DC-DC converter for charging a car battery converts a high voltage battery power source (for example, 42V) to charge a 12V battery.

The DC-DC converter for charging a car battery uses a synchronous rectification method to charge the battery by sequentially turning on two MOSFETs (Metal-Oxide Semiconductor Field Effect Transistors, or MOSFETs) for heat reduction and efficiency. do.

On the other hand, the DC-DC converter for charging a car battery has an output voltage lower than the battery voltage at the initial start-up, so that a reverse current flows from the battery side to the converter.

Therefore, a scheme as shown in FIG. 1 for blocking such reverse current was introduced. As shown in FIG. 1, the reverse current prevention circuit 100 cuts off the current according to the output voltage of the comparator 112 and the comparator 112 that compares the battery Vbat voltage and the output voltage Vout of the converter. It consists of a large-capacity MOSFET 111.

The high-capacity MOSFET 111 is a device for preventing reverse current to block the current flowing from the battery to the converter when the voltage of the battery Vbat compared by the comparator 112 is higher than the output voltage Vout of the converter.

Accordingly, when the voltage of the battery Vbat compared by the comparator 112 is higher than the output voltage Vout of the converter, the PMOS1 is turned off and the reverse current from the body diode of the PMOS1 is blocked. That is, it prevents reverse current from flowing from the battery to the converter.

Incidentally, by the comparator 112, the switching element npn1 is driven when the Vout voltage comp1 (+) is greater than the Vbat voltage comp (-), so that the PMOS1 of the large-capacity MOSFET 111 is conducted.

In addition, the control of the DC-DC converter for charging the battery shown in FIG. 1 is generally a CC-CV charging method.

That is, the DC-DC converter for charging the battery replaces the alternator of the existing vehicle, and controls the output current (Iout) when the converter is overloaded in the overdischarge state of the battery (CC). Or, if the converter is below the maximum output current, the output voltage is controlled (CV).

Here, CV (Constant Voltage) is 12V battery charging voltage control, CC (Constant Current) is 12V battery charging current control.

However, according to the prior art, when the synchronous rectification method is applied to improve efficiency, there is a phenomenon in that a reverse current flows into the converter because the output voltage of the converter is lower than the battery voltage during initial startup. This phenomenon causes damage to the MOSFET and control instability.

In addition, as the high-capacity MOSFET 111 is expensive, there is a problem that the cost of the DC-DC converter for charging an automobile battery increases.

[Advanced technical literature]

[Patent Document]

(Patent Document 1) 1. Korean Patent Publication No. 10-2009-0051505

(Patent Document 2) 2. Korean Registered Patent No. 10-0761584

(Patent Document 3) 3. Korean Patent Publication No. 10-2006-0000647

The present invention has been proposed to solve the problems according to the prior art raised above, even when applying a synchronous rectification method, a micro-hybrid converter and method for preventing reverse current during initial start-up that does not occur reverse current phenomenon The purpose is to provide.

In addition, the present invention prevents a reverse current phenomenon without using an expensive high-capacity MOSFET 111, and a micro-hybrid converter for preventing reverse current during initial start-up in which the cost of a DC-DC converter for charging a vehicle battery does not rise. There are other purposes for providing the method.

The present invention provides a converter for micro-hybrid for preventing reverse current during initial start-up, which solves the instability and control instability of reverse current during initial start-up to achieve the above-mentioned problem.

The micro hybrid converter includes: a first capacitor connected to a high voltage battery;

A first low-capacity MOSFET (Metal Oxide Semiconductor Field-Effect Transistor) connected in parallel with the first capacitor and turned on or off to block or conduct current from a high voltage battery;

A second low-capacity MOSFET connected in series with the first low-capacity MOSFET and turned on or off to block or conduct current from the low-voltage battery;

An inductor connecting between the first low-capacity MOSFET and the second low-capacity MOSFET and the low-voltage battery; And

And a second capacitor connected to the inductor.

In this case, a body diode may be connected to the first low-capacity MOSFET and the second low-capacity MOSFET in parallel.

In this case, the first capacitor may be characterized in that it is a super capacitor.

At this time, when the first low-capacity MOSFET is turned off, it may be characterized in that it operates in a safe boost mode for charging the first capacitor.

At this time, when the second low-capacity MOSFET is turned off, it may be characterized in that it operates in a safety buck mode for charging the low-voltage battery.

In this case, when both the first low-capacity MOSFET and the second low-capacity MOSFET are turned on, it may be characterized in that they are operated in a normal mode buck mode or a boost mode.

At this time, the inductor may be characterized in that it generates an inductor current for checking whether the reverse current flows.

On the other hand, another embodiment of the present invention, a boost mode determination step of determining whether the boost mode as the initial startup is started;

A result of determining the boost mode, if the boost mode is not, a safety buck mode execution step of executing the safety buck mode;

A safe boost mode execution step of executing a safe boost mode if the boost mode is determined as a result of the boost mode;

Determining whether or not reverse current is introduced to determine whether reverse current is introduced;

As a result of determining whether the reverse current flows, the operation stopping step of stopping the operation when there is a reverse current flow; And

It provides a method for preventing a reverse current during initial startup, comprising: a normal mode operation step of operating in a normal buck mode or a normal boost mode if there is no reverse current flow as a result of determining whether the reverse current flows.

At this time, in the safe mode, one of two MOSFETs connected in parallel is turned off and started in an asynchronous manner, and current control is not rated to prevent overheating of the MOSFET due to loss of a body diode connected to the MOSFET. It may be characterized in that it is the first reference value.

At this time, the normal mode may be characterized in that one of the two MOSFETs connected in parallel is turned on and started in a synchronous manner, and the current control is a second reference value that is a rated output.

At this time, the step of determining whether the reverse current flows,

In the buck mode, if the reverse current value is greater than the third reference value, determining in the normal current direction; And

In the boost mode, if the reverse current value is less than the third reference value, the method may further include determining in the normal current direction.

According to the present invention, even when the synchronous rectification method is applied, it is possible to implement a converter for a micro-hybrid that is more stable in control that does not generate a reverse current phenomenon during initial startup.

In addition, another effect of the present invention is that the cost of a DC-DC converter for charging an automobile battery is not increased by preventing a reverse current phenomenon without using an expensive high-capacity MOSFET.

1 is a circuit diagram showing a DC-DC converter for charging a vehicle battery according to the prior art.
2 is a circuit diagram illustrating a micro hybrid converter 200 for preventing reverse current during initial startup according to an embodiment of the present invention.
3 is a circuit diagram showing a method for preventing reverse current during initial startup according to an embodiment of the present invention.
FIG. 4 is an equivalent circuit diagram of the converter 200 for micro-hybrid shown in FIG. 2 and shows a normal buck or boost mode.
FIG. 5 is an equivalent circuit diagram showing a safe buck mode as an asynchronous rectifying buck converter in FIG. 2.
6 is a graph illustrating an equivalent circuit showing the operating principle of the buck converter shown in FIG. 5 and its operation.
FIG. 7 is an equivalent circuit diagram showing a safe boost mode as an asynchronous rectifying boost converter in FIG. 3.
8 is a graph illustrating an equivalent circuit showing the operating principle of the boost converter shown in FIG. 6 and its operation.

The present invention can be variously modified and have various embodiments, and specific embodiments will be illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to a specific embodiment, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

In describing each drawing, similar reference numerals are used for similar components.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from other components.

For example, the first component may be referred to as a second component without departing from the scope of the present invention, and similarly, the second component may be referred to as a first component. The term “and / or” includes a combination of a plurality of related described items or any one of a plurality of related described items.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person skilled in the art to which the present invention pertains.

Terms, such as those defined in a commonly used dictionary, should be interpreted as having meanings consistent with meanings in the context of related technologies, and should not be interpreted as ideal or excessively formal meanings unless explicitly defined in the present application. Should not.

Hereinafter, a micro hybrid converter and method for preventing reverse current during initial startup according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 is a circuit diagram illustrating a micro hybrid converter 200 for preventing reverse current during initial startup according to an embodiment of the present invention. Referring to FIG. 2, the micro-hybrid converter 200 performs reverse current prevention during initial start-up, which resolves inverse current inflow and control instability during initial start-up.

Referring to FIG. 2, the micro hybrid converter 200 includes: a first capacitor 201 connected to a starting generator; A first low-capacity MOSFET (Metal Oxide Semiconductor Field-Effect Transistor) 203-1 connected in parallel with the first capacitor 201 and turned on or off to block or conduct current from the high voltage battery 210; A second low-capacity MOSFET (203-2) connected in series with the first low-capacity MOSFET and turned on or off to interrupt or conduct current from the low-voltage battery; And an inductor 205 connecting between the first low-capacity MOSFET 203-1 and the second low-capacity MOSFET 203-2 and the low-voltage battery 220.

The first and second low-capacity MOSFETs 203-1 and 203-2 are connected in parallel and are low-capacity. Metal oxide semiconductor field effect transistors (MOS field-effect transistors) are the most common field effect transistors (FETs) in digital and analog circuits.

The MOSFET is composed of a channel of an N-type semiconductor or a P-type semiconductor material (refer to a semiconductor device), and according to this material, a device having both characteristics of NMOSFET or PMOSFET is classified as a complementary MOSFET (cMOSFET). Or, nMOSFET, pMOSFET, NMOS FET, PMOS FET, nMOS FET, pMOS FET. etc ..

Further, first and second body diodes 203-1 'and 203-2' are connected in parallel to the first and second low-capacity MOSFETs. The first and second body diodes 203-1 'and 203-2' have a constant current characteristic to conduct current only in one direction. Therefore, it performs a function of blocking reverse current.

The inductor 205 generates an inductor current for checking whether a reverse current flows.

In addition, the first capacitor 201 becomes a super capacitor, and is a component that is intended to be used for the purpose of a battery, with an emphasis on the performance of the capacitor, especially the capacity of the capacitor.

In general, the DC-DC converter performs a function of charging the low voltage battery 220 and supplying an electric load, or charging the super capacitor 201 in an emergency.

That is, a buck mode (Step-Down, high voltage to low voltage power conversion) or a boost mode (Step-Up, low voltage to high voltage power conversion) is performed.

In buck mode, the electrical energy flow is:

Starter Generator-> Inverter-> Super Capacitor-> DC / DC Converter-> 12V Battery

The electrical energy flow in boost mode is as follows.

12V battery-> DC / DC converter-> Super capacitor

Therefore, when both of the first low-capacity MOSFET 203-1 and the second low-capacity MOSFET 203-2 are turned on, they are operated in a normal mode buck mode or a boost mode. A diagram showing this is shown in FIG. 4. 4 will be described later.

In addition, when the second low-capacity MOSFET 203-2 is turned off, it operates in a safety buck mode for charging the low-voltage battery 207. A diagram showing this safety buck mode is illustrated in FIG. 5 and will be described later.

In addition, when the first low-capacity MOSFET 203-1 is turned off, the super capacitor 201 operates in a safe boost mode. A diagram showing this is shown in FIG. 7. This will be described later.

3 is a circuit diagram showing a method for preventing reverse current during initial startup according to an embodiment of the present invention. Referring to FIG. 3, as the initial start-up starts, the converter (200 in FIG. 2) starts operation, and it is determined whether it is in the boost mode (step S310). That is, when the mode is determined, the buck mode charges the low voltage battery 220. Alternatively, the boost mode performs emergency charging by discharging the supercapacitor, which is the first capacitor 201.

As a result of the boost mode determination, if it is not the boost mode, the safety buck mode is executed (step S320).

As a result of the boost mode determination, if it is the boost mode, the safe boost mode is executed (step S330). In the case of the safe mode, the first and second low-capacity MOSFETs 203-1 and 203-2 are started asynchronously, that is, PWM OFF, and the body diodes 203-1 'and 203- of the MOSFETs 203-1 and 203-2 2 ') to eliminate the occurrence of reverse current due to the use of diodes.

In addition, at this time, the current control (C.C: Current Control) is the first reference value (for example, 50A) rather than the rated output to prevent overheating of the MOSFET due to diode loss.

It is determined whether or not reverse current flows in the safe mode (safe buck mode or safe boost mode) (steps S321 and S331).

As a result of determining whether the reverse current flows, if there is a reverse current flow, the operation is stopped (step S340). Incidentally, if the inductor current IL is greater than the third reference value (for example, 0 may be included) in the buck mode, it is determined in the normal current direction, and the normal buck mode is executed (step S350).

On the other hand, if the inductor current IL is smaller than the third reference value (for example, 0 may be included) in the boost mode, the current is determined in the normal current direction, and the normal boost mode is executed (step S360).

Incidentally, as a result of determining whether the reverse current flows, if there is no reverse current flow, it operates in a normal buck mode or a normal boost mode.

At this time, in the normal buck mode or the normal boost mode, the first and second low-capacity MOSFETs 203-1 and 203-2 operate in a synchronous rectification method, that is, PWM ON, and the current control (CC) is a second reference value that is rated output. (For example, it becomes 110A).

FIG. 4 is an equivalent circuit diagram of the converter 200 for micro-hybrid shown in FIG. 2 and shows a normal buck or boost mode. 4, the pulse width modulation signal (PWM_Q1) is applied to the base of the first low-capacity MOSFET (203-1), and the pulse width modulation (PWM_Q2) is applied to the base of the second low-capacity MOSFET (203-2). .

Here, Q1 and Q2 are MOSFETs that include a body drain diode, and are circuits that supply / disconnect the voltage on the source side to the drain side.

FIG. 5 is an equivalent circuit diagram showing a safe buck mode as an asynchronous rectifying buck converter in FIG. 2. Referring to FIG. 5, only the body diode operates with the second low-capacity MOSFET 203-2 turned off. Thus, the current proceeds from left to right as in the direction of the arrow.

6 is a graph illustrating an equivalent circuit showing the operating principle of the buck converter shown in FIG. 5 and its operation. Referring to FIG. 6, the left side shows equivalent circuits 600 and 610, and the right graph 620 describes the operation.

FIG. 7 is an equivalent circuit diagram showing a safe boost mode as an asynchronous rectifying boost converter in FIG. 3. Referring to FIG. 7, only the body diode operates while the first low-capacity MOSFET 203-1 is turned off. Therefore, the current travels from right to left as in the direction of the arrow.

8 is a graph illustrating an equivalent circuit showing the operating principle of the boost converter shown in FIG. 6 and its operation. 8, the left side shows the equivalent circuits 800 and 810, and the right graph 820 describes the operation.

100: reverse current prevention circuit
111: High-capacity MOSFET (Metal Oxide Semiconductor Field-Effect Transistor)
112: comparator
200: micro hybrid converter
201: first capacitor
203-1: 1st low-capacity MOSFET
203-2: Second low-capacity MOSFET
205: inductor
207: second capacitor
210: high voltage battery
600, 610, 800, 810: equivalent circuit of micro hybrid converter

Claims (7)

A first capacitor connected to the high voltage battery;
A first metal oxide semiconductor field-effect transistor (MOSFET) connected in parallel with the first capacitor and turned on or off to block or conduct current from a high voltage battery;
A second MOSFET connected in series with the first MOSFET and turned on or off to block or conduct current from a low voltage battery;
An inductor connecting between the first MOSFET and the second MOSFET and the low voltage battery; And
And a second capacitor connected to the inductor.
A body diode is connected in parallel to the first MOSFET and the second MOSFET, and the first capacitor is a super capacitor,
The inductor generates an inductor current for checking whether a reverse current flows,
During the initial start-up, one of the first and second MOSFETs is turned off to start in an asynchronous manner, and the current control is not the rated output to prevent overheating of the MOSFET due to loss of a body diode connected to the MOSFET. Micro-hybrid converter for preventing reverse current at initial start, characterized in that the reference value.
According to claim 1,
A converter for micro-hybrid for preventing reverse current during initial start-up, wherein the first MOSFET is operated in a first boost mode for charging the first capacitor when the first MOSFET is turned off.
According to claim 1,
A converter for micro-hybrid for preventing reverse current during initial start-up, wherein the second MOSFET is operated in a first buck mode for charging the low-voltage battery when the second MOSFET is turned off.
According to claim 1,
When the first MOSFET and the second MOSFET are started in a synchronous manner, the converter for micro-hybrid for preventing reverse current during initial startup, characterized in that it operates in a second buck mode or a second boost mode.
As a method for preventing a reverse current during the initial start-up of the micro-hybrid converter, the micro-hybrid converter,
A first capacitor connected to the high voltage battery;
A first MOSFET (Metal Oxide Semiconductor Field-Effect Transistor) connected in parallel with the first capacitor and turned on or off to block or conduct current from a high voltage battery;
A second MOSFET connected in series with the first MOSFET and turned on or off to block or conduct current from a low voltage battery;
An inductor connecting between the first MOSFET and the second MOSFET and the low voltage battery; And
And a second capacitor connected to the inductor.
A body diode is connected in parallel to the first MOSFET and the second MOSFET, and the first capacitor is a super capacitor,
The inductor generates an inductor current for checking whether a reverse current flows,
The above method,
A boost mode determination step of determining whether it is in the boost mode as the initial startup starts;
A first buck mode execution step of turning off the second MOSFET and executing a first buck mode for charging the low voltage battery if the boost mode is not determined as a boost mode;
A result of determining the boost mode, if it is a boost mode, a first boost mode execution step of turning off the first MOSFET and executing a first boost mode for charging the first capacitor;
Determining whether or not reverse current is introduced to determine whether reverse current is introduced;
As a result of determining whether the reverse current flows, the operation stopping step of stopping the operation when there is a reverse current flow; And
It includes the step of operating in a second buck mode or a second boost mode for starting the first and second MOSFETs in a synchronous manner if there is no reverse current flow as a result of determining whether the reverse current flows.
During initial start-up, one of the first and second MOSFETs is turned off to start in an asynchronous manner, and the current control is not a rated output to prevent overheating of the MOSFET due to loss of a body diode connected to the MOSFET. A method of preventing reverse current at initial startup, characterized in that it is a reference value.
The method of claim 5,
In the case of the second buck mode and the second boost mode, the first and second MOSFETs are started in a synchronous current method, and the current control is a second reference value that is a rated output.
The method of claim 5,
The determining whether the reverse current flows,
In the first buck mode, if the reverse current value is greater than the third reference value, determining in the normal current direction; And
In the first boost mode, when the reverse current value is less than the third reference value, the method further comprising determining in the normal current direction.

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