TWI477052B - Forward power converter - Google Patents

Description

Forward power converter

The present invention relates to a power conversion technique, and more particularly to a forward power converter for an adaptive regulation function.

In order to enable normal operation of electronic devices (such as desktop personal computers, notebook personal computers, etc.), it is necessary to use a power converter to rectify and filter the AC voltage. To provide a stable DC voltage for use in electronic devices. As shown in FIG. 1, FIG. 1 is a schematic diagram of a conventional forward power converter 10. Referring to FIG. 1, the forward power converter 10 is composed of a transformer T, diodes D1 and D2, a storage inductor L, and a filter capacitor C.

In general, in the storage phase of the forward power converter 10, the primary side P of the transformer T receives the (AC) input voltage V _IN and reacts twice in the transformer T. The alternating voltage of the secondary side S (determined by the turns ratio of one of the transformers T and the secondary side) stores the electrical energy on the energy storage inductor L via the rectification of the diode D1 and the filtering of the filter capacitor C. . Then, in the discharging phase of the forward power converter 10, since the primary side P of the transformer T does not receive the (AC) input voltage V _IN , so that the storage inductor L is stored at this time. The electrical energy is released via the diode D2 and the filter capacitor C, thereby providing a (direct current) output voltage V _OUT for use by the electronic device LD.

However, in the architecture of the forward power converter 10, the forward voltage drop across the diodes D1 and D2 causes some degree of unavoidable conduction loss, thereby The diodes D1 and D2 are made a key component in the forward power converter 10 to generate power loss. In addition, since the stability of the (direct current) output voltage V _OUT provided by the conventional forward power converter 10 is so low, it often deviates from the power supply specification defined by the electronic device LD.

In view of this, the present invention provides a forward power converter having an adaptive adjustment function to solve the problems described in the prior art.

The forward power converter provided by the present invention includes: a transformer having a primary side and a secondary side, wherein the primary side is for intermittently receiving an input voltage; and the first transistor is coupled to the first transistor a first end of the secondary side, wherein the gate is configured to receive the first control voltage when the primary side receives the input voltage; and the second transistor has a drain coupled to the source of the first transistor a source, a source coupled to the second end of the secondary side and a ground potential, and a gate thereof for receiving a second control voltage when the primary side does not receive the input voltage; a storage inductor, The first end is coupled to the source of the first transistor, and the second end is configured to provide an output voltage; the first filter capacitor is first The end is coupled to the second end of the energy storage inductor, and the second end is coupled to the ground potential; and the adjusting unit is coupled to the first end of the first filter capacitor and the gate of the second transistor for Detecting the output voltage when the input side does not receive the input voltage, and correspondingly generating and changing the second control voltage to the gate of the second transistor according to a preset adjustment rate of the output voltage pole.

In an embodiment of the invention, the forward power converter further includes: a second filter capacitor, which is connected to the first filter capacitor.

In an embodiment of the invention, the first filter capacitor and the second filter capacitor are respectively polar capacitors.

In an embodiment of the invention, the first transistor and the second transistor are respectively N-type transistors.

In an embodiment of the invention, the preset adjustment rate determines an upper limit value, a lower limit value, and an interval value of the output voltage, and when the adjustment unit detects that the output voltage is higher than the upper limit value And, the adjusting unit correspondingly generates and reduces the magnitude of the second control voltage to the gate of the second transistor, thereby reducing the output voltage to the interval value. In addition, when the adjusting unit detects that the output voltage is lower than the lower limit value, the adjusting unit correspondingly generates and raises the magnitude of the second control voltage to the gate of the second transistor, thereby The output voltage is to the interval value.

In an embodiment of the invention, the time during which the first transistor is turned on in response to the first control voltage is substantially shorter than the time at which the second transistor is turned on in response to the second control voltage.

Based on the above, the present invention mainly utilizes the parasitic diode of the N-type transistor. The body replaces the role of the traditional diode component. In this way, not only can the unnecessary conduction loss be greatly reduced, but also the overall power loss of the forward power converter can be reduced. On the other hand, the present invention further utilizes an adjustment unit to adjust the output voltage provided by the forward power converter, thereby improving the stability of the supplied output voltage to meet the power supply specifications defined by the electronic device.

It is to be understood that the foregoing general description and claims

Reference will now be made in detail be made to the embodiments of the invention In addition, wherever possible, the same reference numerals in the drawings

2 is a schematic diagram of a forward power converter 20 according to an embodiment of the invention. Referring to FIG. 2, the forward power converter 20 may include a transformer T, transistors M1 and M2 (for example, all N-type transistors, hereinafter referred to as a transistor N). A type of transistor), a storage inductor L, filter capacitors C1 and C2, and a regulation unit 201.

In the present embodiment, the transformer T has a primary side P and a secondary side S, and the primary side P of the transformer T is used to intermittently receive (alternate) the input voltage (AC input). Voltage)V _IN . The drain of the N-type transistor M1 is coupled to the first end of the secondary side S of the transformer T, and the gate of the N-type transistor M1 is used for receiving the primary side P of the transformer T. (AC) receives the first control voltage V _CS1 when the input voltage V _IN . Here, the N-type transistor M1 may also be referred to as a forward rectifier.

The drain of the N-type transistor M2 is coupled to the source of the N-type transistor M1, and the source of the N-type transistor M2 is coupled to the second end of the secondary side S of the transformer T and the ground potential GND, and the gate of the N-type transistor M2 is used to receive the second control voltage V _CS2 when the primary side P of the transformer T does not receive the (AC) input voltage V _IN . Here, the N-type transistor M2 may also be referred to as a free-wheel rectifier. In the present embodiment, the time during which the N-type transistor M1 is turned on in response to the first control voltage V _CS1 is substantially shorter than the time during which the N-type transistor M2 is turned on in response to the second control voltage V _CS2 . Basically, the time ratio of the N-type transistors M1 and M2 to be turned on may be 3:7, but is not limited thereto, and other ratios such as 2:8, 3.5:6.5 can be used.

The first end of the storage inductor L is coupled to the source of the N-type transistor M1, and the second end of the storage inductor L is used to provide the output voltage V _OUT . The filter capacitors C1 and C2 are connected in parallel and are all polar capacitors (for example, electrolytic capacitors, but are not limited thereto). The first end of the filter capacitor C1 is coupled to the second end of the storage inductor L, and the second end of the filter capacitor C1 is coupled to the ground potential GND.

The adjusting unit 201 is coupled to the first end of the filter capacitor C1 and the gate of the N-type transistor M2 for detecting the output voltage V _OUT when the primary side P of the transformer T does not receive the (AC) input voltage V _IN , and and correspondingly generate a second control voltage V _CS2 changes to the gates of N-type transistor M2 is adjusted according to the preset rate of the output voltage V _OUT (predetermined regulation ratio).

In the present embodiment, the preset adjustment rate determines the output voltage V _OUT of the output voltage V _OUT of the upper limit value (upper limit value), the lower limit value (lower limit value) and the value of Interval (interval value). For example, if the output voltage V _{OUT is} set to 5V and the preset regulation of the output voltage V _OUT is ±2%, the upper limit of the output voltage V _OUT is 5.1V; the lower limit of the output voltage V _OUT It is 4.9V; the interval value of the output voltage V _OUT is 4.9V~5.1V.

Moreover, when the adjusting unit 201 detects that the output voltage V _{OUT is} higher than the upper limit value, the adjusting unit 201 correspondingly generates and reduces the magnitude of the second control voltage V _CS2 to the gate of the N-type transistor M2, thereby Reduce the output voltage V _OUT to the interval value. On the other hand, when the adjusting unit 201 detects that the output voltage V _{OUT is} lower than the lower limit value, the adjusting unit 201 correspondingly generates and raises the magnitude of the second control voltage V _CS2 to the gate of the N-type transistor M2. This in turn increases the output voltage V _OUT to the interval value.

Based on the above, in the storage phase of the forward power converter 20, the primary side P of the transformer T receives the (AC) input voltage V _IN and reacts to the AC voltage on the secondary side S of the transformer T. (determined by the turns ratio of one of the transformers T and the secondary side) in response to the turn-on of the N-type transistor M1 (when the N-type transistor M2 is in a turn-off state), The rectification of the parasitic diode of the N-type transistor M1 and the filtering of the filter capacitors C1 and C2 to store electrical energy on the storage inductor L.

Then, in the discharging phase of the forward power converter 20, since the primary side P of the transformer T does not receive the (AC) input voltage V _IN , so that the storage inductor L is stored at this time. The electric energy is supplied in response to the conduction of the N-type transistor M2 (when the N-type transistor M1 is in the off state), and is released via the parasitic diode of the N-type transistor M2 and the filter capacitors C1 and C2, thereby providing (DC The output voltage V _{OUT is used} by the electronic device LD. Wherein forward power converter output voltage V _OUT 20 can be expressed as the following equation _{1: V OUT = V L -Vds} ......... Formula 1

Wherein, V _L is the voltage of the storage inductor L, Vds is the turn-on voltage of the N-type transistor M2, and the turn-on voltage Vds of the N-type transistor M2 can be expressed as the following formula 2 : Vds=I _Load ^* Rds-on...... ...Form 2

Among them, I _Load is the output current of the forward power converter 20, and Rds-on is the on-resistance value of the N-type transistor M2.

At the same time, the adjustment unit 201 starts to detect the supplied output voltage V _OUT (here, the output voltage V _OUT is 5V, and the preset adjustment rate of the output voltage V _OUT is ±2% as an example. Be explained). Once the adjustment unit 201 detects that the output voltage V _{OUT is} higher than the upper limit value (that is, higher than 5.1V), the adjustment unit 201 correspondingly generates and reduces the magnitude of the second control voltage V _CS2 to the N-type power. The gate of crystal M2, which in turn reduces the output voltage V _OUT to the interval value (ie, above 4.9V to 5.1V).

More specifically, based on the above formulas 1 and 2 , when the second control voltage V _CS2 received by the gate of the N-type transistor M2 falls, the on-resistance value Rds-on of the N-type transistor M2 increases. . As a result, the turn-on voltage Vds of the N-type transistor M2 is increased, so that the supplied output voltage V _OUT drops to the interval value (that is, higher than 4.9V~5.1V), that is, V _CS2 ↓, Rds-on↑, Vds↑, V _OUT ↓.

On the other hand, when the adjusting unit 201 detects that the output voltage V _{OUT is} lower than the lower limit value (that is, higher than 4.9V), the adjusting unit 201 correspondingly generates and raises the size of the second control voltage V _CS2 . The gate of the N-type transistor M2, in turn, increases the output voltage V _OUT to the interval value (ie, above 4.9V to 5.1V). More specifically, based on the above formulas 1 and 2 , when the second control voltage V _CS2 received by the gate of the N-type transistor M2 rises, the on-resistance value Rds-on of the N-type transistor M2 decreases. . As a result, the turn-on voltage Vds of the N-type transistor M2 will decrease, so that the supplied output voltage V _OUT will rise to the interval value (that is, higher than 4.9V~5.1V), that is, V _CS2 ↑, Rds-on↓, Vds↓, V _OUT ↑.

It can be seen from the above that the present invention mainly utilizes the parasitic diodes of the N-type transistors M1 and M2 to replace the roles of the conventional diode elements. In this way, not only the unnecessary conduction loss can be greatly reduced, but also the power loss of the forward power converter 20 as a whole can be reduced. On the other hand, the present invention further utilizes the adjustment unit 201 to regulate the output voltage V _OUT provided by the forward power converter 20, thereby improving the stability of the supplied output voltage V _OUT , thereby The power specification defined by the electronic device LD is satisfied. In other words, the present invention utilizes different gate voltages applied to the N-type transistor M2 to cause the N-type transistor M2 to generate different on-resistance values Rds-on, thereby achieving adjustment of the supplied output voltage V. The purpose of _OUT .

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims. In addition, any of the objects or advantages or features of the present invention are not required to be achieved by any embodiment or application of the invention. In addition, the abstract sections and headings are only used to assist in the search of patent documents and are not intended to limit the scope of the invention.

10, 20‧‧‧ directional power converter

T‧‧‧Transformer

Primary side of the P‧‧‧ transformer

Secondary side of the S‧‧‧ transformer

L‧‧‧ storage inductor

C, C1, C2‧‧‧ filter capacitor

D1, D2‧‧‧ diode

M1, M2‧‧‧N type transistor

LD‧‧‧electronic device

V _IN ‧‧‧ input voltage

V _OUT ‧‧‧ output voltage

V _CS1 , V _CS2 ‧‧‧ control voltage

I _Load ‧‧‧Output current

GND‧‧‧ Ground potential

The following drawings are a part of the specification of the invention, and illustrate the embodiments of the invention

FIG. 1 is a schematic diagram of a conventional forward power converter 10.

2 is a schematic diagram of a forward power converter 20 in accordance with an embodiment of the present invention.

20‧‧‧ directional power converter

T‧‧‧Transformer

Primary side of the P‧‧‧ transformer

Secondary side of the S‧‧‧ transformer

L‧‧‧ storage inductor

C1, C2‧‧‧ filter capacitor

M1, M2‧‧‧N type transistor

LD‧‧‧electronic device

V _IN ‧‧‧ input voltage

V _OUT ‧‧‧ output voltage

V _CS1 , V _CS2 ‧‧‧ control voltage

I _Load ‧‧‧Output current

GND‧‧‧ Ground potential

Claims (6)

A forward power converter includes: a transformer having a primary side and a secondary side, wherein the primary side is for intermittently receiving an input voltage; and a first transistor is coupled to the first transistor a first end of the secondary side, and a gate thereof for receiving a first control voltage when the primary side receives the input voltage; a second transistor having a drain coupled to the first transistor a source, the source is coupled to the second end of the secondary side and a ground potential, and the gate is configured to receive a second control voltage when the primary side does not receive the input voltage; a storage inductor The first end is coupled to the source of the first transistor, and the second end is configured to provide an output voltage. The first filter capacitor has a first end coupled to the second end of the energy storage inductor. The second end is coupled to the ground potential; and an adjustment unit coupled to the first end of the first filter capacitor and the gate of the second transistor for receiving the input on the primary side Detecting the output voltage at a voltage and corresponding to the real estate according to a preset adjustment rate of the output voltage And changing the second control voltage to the gate of the second transistor, wherein the preset adjustment rate determines an upper limit value, a lower limit value and an interval value of the output voltage, and when the adjusting unit detects the When the output voltage is higher than the upper limit value, the adjusting unit correspondingly generates and reduces the magnitude of the second control voltage to the gate of the second transistor, thereby reducing the output voltage to the interval value. The forward power converter of claim 1, further comprising: a second filter capacitor, which is connected to the first filter capacitor. The forward power converter of claim 2, wherein the first filter capacitor and the second filter capacitor are respectively a polar capacitor. The forward power converter of claim 1, wherein the first transistor and the second transistor are respectively an N-type transistor. The forward power converter of claim 1, wherein when the adjusting unit detects that the output voltage is lower than the lower limit, the adjusting unit correspondingly generates and raises the second control voltage. The size is given to the gate of the second transistor, thereby boosting the output voltage to the interval value. The forward power converter of claim 1, wherein the first transistor reacts to the first control voltage to be turned on for substantially shorter time than the second transistor reacts to the second control voltage And the time of conduction.