TW201349725A - High efficiency power converter - Google Patents

Abstract

A high efficiency power converter includes a first capacitor, a transformer, a first switch, a sensing resistor, and a controller. The transformer includes a primary winding and a secondary winding. The first capacitor is used for receiving and stabilizing a direct current voltage. The transformer boosts the direct current voltage according to a turn ratio of the primary winding to the secondary winding. The sensing resistor is used for sensing current flowing through the first switch. The controller is used for generating a control signal according to the current to control turning-on and turning-off of the first switch, detecting the current, and outputting a dimming signal. A second terminal of the primary winding is coupled to a second terminal of the secondary winding, or the second terminal of the primary winding is coupled to the second terminal of the secondary winding through a first diode.

Description

High efficiency power converter

The invention relates to a power converter, in particular to a primary side coil coupled to a secondary side coil, or a primary side coil coupled to a secondary side coil through a first diode to improve power converter conversion. Efficiency and reduces the high efficiency power converter on the first switch due to chopping caused by the secondary side coil induction.

Please refer to FIG. 1. FIG. 1 is a schematic diagram of a flyback power converter 100 for the prior art. As shown in FIG. 1, the transformer 102 is configured to boost the DC voltage VIN to an output voltage VOUT according to the turns ratio of the primary side coil 1022 and the secondary side coil 1024, wherein the output voltage VOUT is used to A load 104 (eg, a string of light emitting diodes) is driven. A sense resistor 106 is used to sense a current ID flowing through a first switch 108. Therefore, a controller 110 can generate a control signal CS to control the opening and closing of the first switch 108 according to the current ID. In addition, the controller 110 can also generate a dimming signal DS to a second switch 112 to control the brightness of a string of LEDs.

Although the transformer 102 can increase the boosted DC voltage VIN to the output voltage VOUT according to the turns ratio of the primary side coil 1022 and the secondary side coil 1024, the energy of the direct current voltage VIN is not completely converted to the secondary side coil 1024. Therefore, the conversion efficiency of the flyback power converter 100 is not very high. As such, the flyback power converter 100 Not a good power converter for a user.

An embodiment of the invention provides a high efficiency power converter. The high efficiency power converter comprises a first capacitor, a transformer, a first switch, a sensing resistor and a control circuit, wherein the transformer comprises a primary side coil and a secondary side coil. The first capacitor has a first end for receiving a DC voltage, and a second end for coupling to a ground end; the primary side coil has a first end coupled to the first capacitor a first end, and a second end; the second side coil has a first end, and a second end; the first switch has a first end coupled to the second end of the primary side coil, a second end, and a third end; the sensing resistor has a first end coupled to the third end of the first switch, and a second end coupled to the ground end, wherein the sensing resistor The control circuit has a first end coupled to the second end of the first switch for generating the current according to the current flowing through the first switch. a control signal for controlling the opening and closing of the first switch, a second end for detecting the current, a third end, and a fourth end for outputting a dimming signal; the primary side coil The second end of the primary side coil is coupled to the second end of the secondary side coil, or the second end of the primary side coil is coupled to the first diode The second end of the secondary coil.

The present invention provides a high efficiency power converter. The high efficiency power converter is coupled to the second end of the secondary side coil by using the second end of the primary side coil, or the second end of the primary side coil is coupled to the second end through the first diode a second end of the secondary side coil to increase the conversion efficiency of the high efficiency power converter and lower the first switch because The chopping caused by the secondary side coil induction. In addition, the control circuit of the high efficiency power converter can generate an overcurrent protection according to the current flowing through the first switch, and generate an overvoltage protection according to the first voltage generated by a voltage dividing circuit. In addition, a series of light-emitting diodes comprise a plurality of sets of light-emitting diodes connected in series, so the current flowing through the plurality of sets of light-emitting diodes connected in series will be the same. Therefore, the present invention can improve the conversion efficiency of the high-efficiency power converter, reduce the cost of the high-efficiency power converter (because the first switch does not need to be a high-voltage switch), and can enable multiple sets of series-connected light-emitting diodes. The brightness of each of the light-emitting diodes is the same.

Please refer to FIG. 2, which is a schematic diagram of a high efficiency power converter 200 according to an embodiment of the invention. The high-efficiency power converter 200 includes a first capacitor 202, a transformer 204, a first switch 206, a sensing resistor 208, and a control circuit 210. The transformer 204 includes a primary side coil 2042 and a secondary side coil. 2044, and the sensing direction of the primary side coil 2042 and the sensing direction of the secondary side coil 2044 are opposite. The first capacitor 202 has a first end for receiving the DC voltage VDC and a second end for coupling to a ground GND. The primary side coil 2042 has a first end coupled to the first end of the first capacitor 202 and a second end. The second side coil 2044 has a first end and a second end. The first switch 206 has a first end coupled to the second end of the primary side coil 2042, a second end, and a third end. The sensing resistor 208 has a first end coupled to the third end of the first switch 206, and a second end coupled to the ground GND, wherein the sensing resistor 208 is configured to sense the flow through the first switch A current ID of 206. The control circuit 210 has a first end coupled to the second end of the first switch 206 The terminal 214 generates a control signal CS to control the opening and closing of the first switch 206, and a second terminal for detecting the current according to a sensing voltage VS generated by the current ID flowing through the first switch 206. The ID, a third end, and a fourth end are used to output a dimming signal DS, wherein the control circuit 210 is of the type LD 7889, and the control signal CS is a one-on time and a cut-off time. Pulse width modulation signal. As shown in FIG. 2, the second end of the primary side coil 2042 is coupled to the second end of the secondary side coil 2044 through a first diode 212. However, in another embodiment of the present invention, the second end of the primary side coil 2042 is directly coupled to the second end of the secondary side coil 2044.

As shown in FIG. 2, the high efficiency power converter 200 further includes a rectifier 214, a voltage dividing circuit 216, a second diode 218, a second capacitor 220, a second switch 221, and a magnetizing inductance Cc. The rectifier 214 has a first end coupled to the positive end of an AC power source SAC for receiving an AC voltage VAC, and a second end coupled to the first end of the first capacitor 202 for outputting a DC voltage VDC. a third end coupled to the negative end of the AC power supply SAC and a fourth end coupled to the ground GND. The magnetizing inductor Cc has a first end coupled to the first end of the first capacitor 202 and a second end coupled to the second end of the primary side coil 2042. The second diode 218 has a first end coupled to the first end of the secondary coil 2044, and a second end for outputting an output voltage VOUT to the first end of the string of LEDs 222. The second capacitor 220 has a first end coupled to the second end of the second diode 218, and a second end coupled to the ground GND; the voltage dividing circuit 216 has a first end, coupled Connected to the second end of the second diode 218, a second end for outputting a first voltage V1 to the third end of the control circuit 210 and a third end coupled to the ground according to the output voltage VOUT Terminal GND; second switch The 221 has a first end for coupling to the second end of the string of LEDs 222, and a second end coupled to the fourth end of the control circuit 210 for receiving the dimming signal DS, and a The third end is coupled to the ground GND. Because the dimming signal DS can be a pulse width modulation signal, a high potential signal or a low potential signal, the second switch 221 can control the brightness of a string of LEDs 222 according to the dimming signal DS. That is, the second switch 221 can adjust the current ILED flowing through the string of the LEDs 222 according to the dimming signal DS to control the brightness of the string of LEDs 222. In addition, a series of light-emitting diodes 222 includes a plurality of sets of light-emitting diodes connected in series, so the current flowing through the plurality of sets of series-connected light-emitting diodes is equal to the current ILED. Thus, the brightness of each of the plurality of LEDs connected in series will be the same.

As shown in FIG. 2, the rectifier 214 is for rectifying the AC voltage VAC to generate and output a DC voltage VDC to the primary side coil 2042. The transformer 204 is configured to increase the DC voltage VDC into an output voltage VOUT according to a turns ratio of the primary side coil 2042 and the secondary side coil 2044, wherein the output voltage VOUT is used to drive a string of the LEDs 222. When the first switch 206 is turned on according to the control signal CS, the secondary side coil 2044 is used to store the electrical energy transmitted by the primary side coil 2042, and the second capacitor 220 is used to release the electrical energy stored by the second capacitor 220. A string of light emitting diodes 222 is driven. That is, when the first switch 206 is turned on according to the control signal CS, since the second diode 218 is turned off, the electric energy transmitted by the primary side coil 2042 is stored in the secondary side coil 2044 instead of being transmitted to the output voltage VOUT. . As shown in FIG. 2, the electric energy transmitted from the primary side coil 2042 can be transmitted not only to the secondary side coil 2044 through induction, but also to the secondary side coil 2044 through the first diode 212. In addition, when When the first switch 206 is turned on according to the control signal CS, the first diode 212 can reduce the chopping caused by the secondary side coil 2044 on the first switch 206, and the magnetizing inductance Cc can be used to filter out the first switch 206. The upper surge, so the first switch 206 does not need to be a high voltage switch. When the first switch 206 is turned off according to the control signal CS, the secondary side coil 2044 is configured to release the stored electric energy to simultaneously drive a string of the LEDs 222 and charge the second capacitor 220. That is, when the first switch 206 is turned off according to the control signal CS, since the second diode 218 is turned on, the secondary side coil 2044 can simultaneously drive a string of the LEDs 222 and the pair according to the stored electric energy. The second capacitor 220 is charged. In addition, when the current ID is greater than a predetermined current value, the control circuit 210 can generate an overcurrent protection; when the first voltage V1 is greater than a predetermined value of the voltage, the control circuit 210 can generate an overvoltage protection.

In summary, the high efficiency power converter provided by the present invention is that the second end of the primary side coil is coupled to the second end of the secondary side coil, or the second end of the primary side coil is transmitted through the first diode. The second end of the secondary side coil is coupled to improve the conversion efficiency of the high efficiency power converter and reduce the chopping caused by the secondary side coil induction on the first switch. In addition, the control circuit of the high efficiency power converter can generate overcurrent protection according to the current flowing through the first switch, and generate overvoltage protection according to the first voltage generated by the voltage dividing circuit. In addition, a series of light-emitting diodes comprise a plurality of sets of light-emitting diodes connected in series, so the current flowing through the plurality of sets of light-emitting diodes connected in series will be the same. Therefore, the present invention can improve the conversion efficiency of a high-efficiency power converter, reduce the cost of a high-efficiency power converter (because the first switch does not need to be a high-voltage switch), and can make each of the plurality of sets of light-emitting diodes connected in series The brightness of the diode is the same.

The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be within the scope of the present invention.

100‧‧‧Return-type power converter

102, 204‧‧‧ Transformers

104‧‧‧load

106, 208‧‧‧ sense resistor

108, 206‧‧‧ first switch

110‧‧‧ Controller

112, 221‧‧‧ second switch

200‧‧‧High efficiency power converter

202‧‧‧first capacitor

210‧‧‧Control circuit

212‧‧‧First Diode

214‧‧‧Rectifier

216‧‧‧voltage circuit

218‧‧‧second diode

220‧‧‧second capacitor

222‧‧‧A string of LEDs

1022, 2042‧‧‧ primary side coil

1024, 2044‧‧‧ secondary side coil

CS‧‧‧Control signal

Cc‧‧‧Magnetic inductance

DS‧‧‧ dimming signal

GND‧‧‧ ground

ID, ILED‧‧‧ current

SAC‧‧‧AC power supply

VIN, VDC‧‧‧ DC voltage

VOUT‧‧‧ output voltage

VS‧‧‧Sensor voltage

VAC‧‧‧AC voltage

V1‧‧‧ first voltage

Figure 1 is a schematic diagram of a flyback power converter for the prior art.

Fig. 2 is a schematic view showing a high efficiency power converter according to an embodiment of the present invention.

200‧‧‧High efficiency power converter

202‧‧‧first capacitor

206‧‧‧First switch

204‧‧‧Transformers

208‧‧‧Sensor resistance

210‧‧‧Control circuit

212‧‧‧First Diode

214‧‧‧Rectifier

216‧‧‧voltage circuit

218‧‧‧second diode

220‧‧‧second capacitor

221‧‧‧second switch

222‧‧‧A string of LEDs

2042‧‧‧One-side coil

2044‧‧‧second side coil

CS‧‧‧Control signal

Cc‧‧‧Magnetic inductance

DS‧‧‧ dimming signal

GND‧‧‧ ground

ID, ILED‧‧‧ current

SAC‧‧‧AC power supply

VDC‧‧‧ DC voltage

VOUT‧‧‧ output voltage

VS‧‧‧Sensor voltage

VAC‧‧‧AC voltage

V1‧‧‧ first voltage

Claims (15)

A high-efficiency power converter includes: a first capacitor having a first end for receiving a DC voltage, and a second end for coupling to a ground end; and a transformer comprising: once The side coil has a first end coupled to the first end of the first capacitor, and a second end; and a secondary side coil having a first end and a second end; a first switch a first end coupled to the second end of the primary side coil, a second end, and a third end; a sensing resistor having a first end coupled to the first switch a third end, and a second end coupled to the ground end, wherein the sensing resistor is configured to sense a current flowing through the first switch; and a control circuit has a first end coupled to the first end The second end of the first switch is configured to generate a control signal to control the opening and closing of the first switch according to the current flowing through the first switch, and a second end for detecting the current, a third end, and a fourth end, for outputting a dimming signal; wherein the second end of the primary side coil is coupled to the second A second side coil end or the second end of the primary side coil is through a first diode coupled to the second terminal of the secondary side coil. The high-efficiency power converter of claim 1, further comprising: a rectifier having a first end coupled to a positive end of an AC power source for receiving Receiving an AC voltage, a second end coupled to the first end of the first capacitor for outputting the DC voltage, a third end coupled to the negative end of the AC power source, and a fourth end Coupling to the ground. The high efficiency power converter of claim 1, wherein the secondary side coil is used to store electrical energy when the first switch is turned on according to the control signal. The high efficiency power converter of claim 1, wherein the control signal is a pulse width modulation signal. The high efficiency power converter of claim 4, wherein the pulse width modulation signal comprises an on time and a off time. The high efficiency power converter of claim 1, wherein the control circuit is of the type LD 7889. The high efficiency power converter of claim 1, wherein the control circuit generates an overcurrent protection based on the current. The high efficiency power converter of claim 1, wherein the sensing direction of the primary side coil and the sensing direction of the secondary side coil are opposite. The high efficiency power converter of claim 1 further comprising: a second diode having a first end coupled to the first end of the secondary side coil and a second end for outputting an output voltage to the first end of the string of LEDs; And a second capacitor having a first end coupled to the second end of the second diode and a second end coupled to the ground end. The high-efficiency power converter of claim 9, further comprising: a voltage dividing circuit having a first end coupled to the second end of the second diode and a second end for outputting A first voltage is coupled to the third end of the control circuit, and a third end coupled to the ground end, wherein the control circuit generates an overvoltage protection according to the first voltage. The high efficiency power converter of claim 9, further comprising: a second switch having a first end coupled to the second end of the string of LEDs, a second end coupled The fourth end of the control circuit is configured to receive the dimming signal, and a third end is coupled to the ground end. The high efficiency power converter of claim 9, wherein the second capacitor is configured to release the stored electrical energy to drive the string of light emitting diodes when the first switch is turned on according to the control signal. The high efficiency power converter of claim 9, wherein the secondary side coil is configured to release the stored electrical energy when the first switch is turned off according to the control signal. The string of light emitting diodes is simultaneously driven and the second capacitor is charged. The high efficiency power converter of claim 9, wherein the string of light emitting diodes comprises a plurality of sets of light emitting diodes connected in series. The high-efficiency power converter of claim 1, further comprising: a magnetizing inductor having a first end coupled to the first end of the first capacitor and a second end coupled to the primary side a second end of the coil; wherein the magnetizing inductance is a surge for filtering the first switch.