TW201547175A - AC to DC converter with reduced standby power - Google Patents

Abstract

An exemplary embodiment of the present disclosure provides an AC to DC converter with reduced standby power. The AC to DC Converter comprises a primary winding, a secondary winding, a control circuit, a feedback circuit, and a pulse width modulator, wherein the control circuit further comprises an analog to digital converter and a logic circuit. The output voltage of the secondary winding is digitized by the analog to digital converter. The logic circuit detects the digitized output voltage. The AC to DC converter can avoid affecting the accuracy of the feedback signal, thereby effectively adjust the duty ratio of the pulse width modulation signal. In the standby mode, the AC to DC converter generates a specific output voltage fluctuation ranges, thereby reducing power dissipation during the standby mode.

Description

AC/DC converter that reduces standby power consumption

The present invention relates to an AC to DC converter, and more particularly to an AC/DC converter for reducing standby power consumption.

In the application of consumer electronics, AC to DC converters have been widely used. For example, home appliances or computers need to use AC/DC converters to convert AC power to DC power. However, with the increasing awareness of environmental protection in recent years, and the issue of global warming, forcing energy conservation has become one of the important policies of all countries in the world. Therefore, today's energy-saving is a product performance indicator that is very important for many consumer electronic products. In addition to the power efficiency during normal operation, the power consumption during standby is also an important data. In many countries, the power consumption during standby is included in the national standard, and low standby power consumption is an important selling point for many consumer electronic products.

Referring to FIG. 1, FIG. 1 is a schematic diagram of a conventional AC/DC converter circuit architecture without a standby power supply design.

The AC/DC converter 1 mainly includes a full-bridge rectification filter circuit 101, a primary side coil Wp, a secondary side coil Ws, a changeover switch SW, an output filter circuit 103, a feedback control circuit 105, and a pulse width modulator 107.

The full bridge rectification filter circuit 101 is configured to receive an alternating current (eg, mains) input and convert it into a rectified output. One end of the primary side coil Wp is connected to the full bridge rectifying and filtering circuit 101 for receiving the rectified alternating current output by the full bridge rectifying and filtering circuit 101, The other end of the secondary side coil Wp is connected to the changeover switch SW, and the changeover switch SW controls its switching by the pulse width modulator 107.

According to the switching of the switching switch SW, the primary side coil Wp couples the stored energy to the secondary side coil Ws, and further generates an output voltage across the secondary side coil Ws, and outputs it to the load via the output filter circuit 103 ( Not shown).

The feedback control circuit 105 measures the output voltage on the load to generate a feedback signal and feeds the feedback signal back to the pulse width modulator 107. More specifically, the output voltage provides a divided voltage (not shown) in a resistor divider manner, and the divided voltage drives the voltage regulator TL431 to generate a voltage difference proportional to the divided voltage and the internal reference voltage of the voltage regulator TL431. Feedback signal. Based on the received feedback signal, the pulse width modulator 107 outputs a pulse width modulation signal PWM for controlling the switching frequency of the switching switch SW, thereby affecting the output voltage of the AC/DC converter 1.

Briefly, the pulse width modulator 107 controls the on or off of the switch SW according to the feedback signal to adjust the output voltage. Therefore, when the output voltage is to be increased (when the load is increased), the pulse width modulator 107 increases the duty ratio of the pulse width modulation signal, and when the output voltage is to be reduced (when the load is lowered) The pulse width modulator 107 reduces the duty cycle of the pulse width modulation signal.

Furthermore, how to reduce the power consumption during AC/DC converter conversion standby has become an important research direction of power electronics.

In view of this, an embodiment of the present invention provides an AC/DC converter, which is mainly an analog-to-digital converter and a logic circuit as a control circuit of the AC/DC converter, and an output voltage is controlled by an analog-to-digital converter. The digitization, and thus avoiding the accuracy of the feedback signal when the feedback frequency is lowered, and simultaneously achieving the free control standby state, the output voltage of the AC/DC converter can fluctuate within a certain wide range.

The present invention provides an AC/DC converter for reducing standby power consumption. The AC/DC converter includes a primary side coil, a secondary side coil, a control circuit, a feedback circuit, and a pulse width modulator. One end of the primary side coil is used to receive the input voltage, and the other end is connected to the switch. The secondary side coil is electromagnetically coupled to the primary side coil to sense the voltage at which the output is generated. Wherein, the control circuit mainly comprises an analog digital converter and a logic circuit. The voltage outputted by the secondary side coil is converted into a digitized signal by an analog digital converter, and the digital signal is detected by using a logic circuit, and a control signal is outputted to the feedback circuit according to the digitized signal. The feedback circuit outputs a feedback signal to the pulse width modulator according to the received control signal. The pulse width modulator generates a pulse width modulation signal to control the switching of the switch, wherein the duty ratio of the pulse width modulation signal is controlled by the feedback signal. Therefore, the output voltage of the AC/DC converter is indirectly controlled by adjusting the duty ratio of the pulse width modulation signal controlled by the feedback signal.

In summary, the above-mentioned AC/DC converter can improve the accuracy of the feedback signal by digitizing the output voltage by using an analog digital converter and detecting the digitized output voltage by the logic circuit. , thereby effectively adjusting the duty ratio of the pulse width modulation signal, and by controlling the standby state freely to control the output voltage of the AC/DC converter within a specific fluctuation range, the power consumption of the standby power can be greatly reduced. .

The detailed description of the present invention and the accompanying drawings are to be understood by the claims The scope is subject to any restrictions.

1, 2‧‧‧ AC/DC converter

101, 201‧‧‧ Full Bridge Rectifier Filter Circuit

Wp‧‧‧ primary side coil

Ws‧‧‧ secondary coil

SW‧‧‧Toggle switch

103‧‧‧Output filter circuit

105‧‧‧Feedback control circuit

TL431‧‧‧Voltage regulator

107, 207‧‧‧ pulse width modulator

PWM‧‧‧ pulse width modulation signal

203‧‧‧Control circuit

2031‧‧‧ Analog Digital Converter

2033‧‧‧Logical Circuit

2035‧‧‧Digital Analog Converter

2037‧‧‧Standby command setter

205‧‧‧Return circuit

2051‧‧‧Light emitting elements

2053‧‧‧Light detecting component

S301~S307‧‧‧Step procedure

FIG. 1 is a circuit diagram of a conventional AC/DC converter without a standby power supply design.

2 is a circuit diagram of an AC/DC converter according to an embodiment of the present invention.

FIG. 3 is a flow chart showing the operation of the control circuit of the AC/DC converter in the standby state according to an embodiment of the present invention.

In the following, the invention will be described in detail by way of illustration of various exemplary embodiments of the invention. However, the inventive concept may be embodied in many different forms and should not be construed as being limited to the illustrative embodiments set forth herein. In addition, the same reference numerals may be used in the drawings to represent similar elements.

The AC/DC converter for reducing standby power consumption of the present invention can be widely applied to various electronic devices requiring standby power, such as a server power supply, an external adapter, a battery charger, and a computer mains power supply, and the present invention does not Limited.

The main purpose of the AC/DC converter is to receive an AC voltage input and convert it to output a DC voltage. Please refer to FIG. 2. FIG. 2 is a circuit diagram of an AC/DC converter according to an embodiment of the present invention. The AC/DC converter 2 includes a full-bridge rectification filter circuit 201, a primary side coil Wp, a secondary side coil Ws, a control circuit 203, a feedback circuit 205, and a pulse width modulator 207. The full bridge rectification filter circuit 201 is identical to the full bridge rectification filter circuit 101 of FIG. 1 for receiving an alternating current (eg, mains) input and converting it to a rectified output. Elements of FIG. 2 that are similar to those of FIG. 1 are labeled with similar reference numerals, and thus details thereof will not be described in detail herein.

The first end of the primary side coil Wp is for receiving the input voltage, the second end of the primary side coil Wp is connected to the switch SW; the secondary side coil Ws is electromagnetically coupled to the primary side coil Wp for inducing the output voltage, and The output voltage generated by the secondary side coil Ws can be supplied to a load (not shown) via the filtered output.

The control circuit 203 is electrically connected to the secondary side coil Ws for measuring the output voltage generated by the secondary side coil Ws to generate a control signal to the feedback circuit 205. The control circuit 203 mainly includes an analog digital converter 2031 and a logic circuit 2033. The analog digital converter 2031 is configured to convert the received secondary side coil Ws output voltage into a digital signal, and the logic circuit 2033 is electrically connected to the analog digital position. The converter 2031, the logic circuit 2033 detects and outputs a control signal according to the received digital signal.

Briefly, the output voltage of the secondary side coil Ws is digitally quantized by the analog-to-digital converter 2031, and is detected by the logic circuit 2033 for the digitized output voltage. Therefore, the AC/DC converter 2 detects the digitized signal through the logic circuit 2033 to avoid an error problem caused by components such as the AC/DC converter 2 resistance and inductance, and increases the output voltage amount of the secondary side coil Ws. The accuracy of the measurement.

The feedback circuit 205 is electrically connected to the control circuit 203 for receiving the control signal, and outputs a feedback signal to the pulse width modulator 207 according to the control signal.

For example, the feedback circuit 205 is generally used as an optical coupler, but the invention is not limited thereto. The photocoupler mainly uses a light as a medium to transmit an electrical signal, and a linear optical coupler can be used. The optocoupler feedback circuit is tuned to regulate the current at the output. Therefore, for example, in FIG. 2, the feedback circuit 205 includes a light emitting element 2051 and a light detecting element 2053. The light emitting element 2051 is electrically connected to the control circuit 203, and the light detecting element 2053 is electrically connected to the pulse width modulation. The 207 is configured to receive the optical signal generated by the light emitting element 2051, and the feedback signal output by the feedback circuit 205 is a current signal. Briefly, the feedback circuit 205 adjusts the magnitude of the current of the output signal based on the received control signal. In one embodiment, the light emitting element 2051 can be a light emitting diode (LED), and the light detecting element 2053 is one of a photodiode and a photoelectric crystal, and the invention is not limited thereto.

The pulse width modulator 207 is electrically connected between the feedback circuit 205 and the switch SW, and the pulse width modulator 207 is configured to generate a pulse width modulation signal PWM to control the switching of the switch SW, wherein the pulse wave The duty cycle of the width modulation signal PWM is controlled by the feedback signal.

Briefly, the pulse width modulation signal PWM outputted by the pulse width modulator 207 controls the switching switch SW to be turned on or off, and the duty ratio of the pulse width modulation signal PWM is mainly by the feedback signal. And decided. Since the feedback circuit 205 adjusts the magnitude of the current outputting the feedback signal according to the received control signal, the pulse The width modulator 207 determines the duty ratio of the output pulse width modulation signal PWM by determining the current level of the photodetecting element 2053, thereby indirectly controlling the output voltage of the AC/DC converter 2.

In this embodiment, the pulse width modulator 207 has a FB pin, and the FB pin is used to receive the feedback signal. The pulse width modulator 207 adjusts the output pulse according to the current level received by the FB pin. The duty cycle of the wave width modulation signal PWM. Therefore, when the current levels of the feedback signals are different, the pulse width modulator 207 outputs the pulse width modulation signal PWM of different duty ratios to control the switching frequency of the switching switch SW, thereby achieving control communication. / DC converter 2 for the purpose of voltage regulation.

The switch SW is generally a gold-oxygen half field effect transistor (MOSFET) having a drain connected to the primary side coil Wp and a gate connected to the pulse width modulator 207 for receiving the pulse width modulation signal PWM. In general, the energy stored on the primary side of the AC/DC converter 2 is mainly transmitted to the primary side coil Wp in accordance with the switching of the switching switch SW.

In practice, since the feedback circuit 205 mostly uses an optical coupler, and the optical coupler element can be generally divided into digital or analog forms, it is worth noting that the present invention is not limited thereto. Therefore, in the preferred embodiment of the present invention, the control circuit 203 may further include a digital analog converter 2035, which is electrically equivalent to the digital analog converter 2035, in consideration of the use of the optical coupler component in the analogy form. Connected between the logic circuit 2033 and the feedback circuit 205, the digital analog converter 2035 is configured to receive the control signal and convert the control signal into an analog format output to the feedback circuit 205.

Briefly, the present invention is not limited to the device type of the feedback circuit 205. When the feedback circuit 205 is of a digital type, the control circuit 203 can directly output the control signal in the digitized format to the feedback circuit 205 through the logic circuit 2033; When the feedback circuit 205 is of an analog type, the control circuit 203 may further include a digital analog converter 2035 for converting the output signal of the logic circuit 2033 into an analog signal of an analog format and transmitting the signal to the analog signal. The feedback circuit 205.

In addition, in the preferred embodiment of the present invention, the AC/DC converter 2 further includes a full bridge rectification filter circuit 201. The full bridge rectification filter circuit 201 is electrically connected to the first end of the primary side coil Wp, and the full bridge rectification is performed. The filter circuit 201 is mainly used to receive the mains and is converted into a rectified input voltage to be supplied to the primary side coil Wp.

According to the above, in the circuit structure of the conventional AC/DC converter, the circuit on the secondary side needs to have multiple components such as resistors and capacitors, and the output voltage generated by the secondary side coil is detected by the voltage division method. The size, and then the feedback signal is adjusted to control the pulse width modulator to output a corresponding pulse width modulation signal to control the switching frequency of the switching switch. Therefore, for different voltage quality requirements, in consideration of electronic component errors and the like, the conventional AC/DC converter needs to be calibrated for components such as resistors or capacitors on the secondary side to reduce the output generated by the secondary side coil. The error value of the voltage. In contrast, the present invention provides an AC/DC converter, which is mainly an analog-to-digital converter and a logic circuit as a control circuit of the AC/DC converter, which is generated by a secondary-side coil by an analog-to-digital converter. The output voltage is digitized and detected by a logic circuit on the digitized output voltage. Therefore, the accuracy of the measurement result of the output voltage generated by the secondary side coil can be effectively improved, and the accuracy of controlling the feedback signal can be improved, thereby effectively adjusting the duty ratio of the pulse width modulation signal, thereby achieving The AC/DC converter is used for voltage regulation purposes.

Referring to FIG. 2, in a preferred embodiment of the present invention, the control circuit 203 further includes a standby command setter 2037. The standby command setter 2037 is electrically connected to the logic circuit 2033 for setting whether the AC/DC converter 2 is Perform a standby mode of operation.

Please refer to FIG. 2 and FIG. 3 simultaneously. FIG. 3 is a flow chart showing the operation of the control circuit of the AC/DC converter in the standby state according to an embodiment of the present invention. When the AC/DC converter 2 performs the standby mode of operation, the logic circuit 2033 of the control circuit 203 compares the digital signal with the first threshold and the second threshold to output a corresponding control signal, thereby controlling the pulse width modulator. 207 output pulse width modulation signal PWM, and the first critical value is greater than the second critical value.

In detail, when the AC/DC converter 2 performs the standby mode, the logic circuit 2033 first compares the digital signal with the first threshold to determine whether the digital signal is greater than or equal to the first threshold. If the digital signal is less than the first critical value, then step S307 is reached. In step 307, the control circuit 203 outputs a corresponding control signal based on the current digital signal, thereby adjusting the output voltage of the AC/DC converter 2, and then returns to step S301. If the digital signal is greater than or equal to the first critical value, the process proceeds to step S303, and the control circuit 203 further controls the pulse width modulator 207 to stop outputting the pulse width modulation signal PWM. Following the step S305, the logic circuit continues to compare the digital signal with the second threshold until the digital signal reaches less than or equal to the second threshold, and the control circuit 203 continues the operation of step S303. In step S305, when the digital signal is less than or equal to the second critical value, the process proceeds to step S307. Step 307, the control circuit 203 outputs a corresponding control signal according to the current digital signal, thereby adjusting and increasing the output voltage of the AC/DC converter 2, and returning to step S301, comparing again whether the digital signal is greater than or equal to the first critical value. However, in step S301, if the digital signal is not greater than or equal to the first threshold, step S307 is continued, and the control circuit 203 outputs a corresponding control signal according to the digital signal, thereby adjusting and increasing the output of the AC/DC converter 2. The voltage until the digital signal reaches greater than or equal to the first critical value.

For example, the first threshold may be set to +12V, and the second threshold may be set to +8V, but the invention is not limited thereto. In practice, when the AC/DC converter of the present invention enters the standby mode of operation, it is determined by the control circuit whether the current output voltage reaches +12 V (step S301), and if +12 V is reached, the control circuit output corresponds to The control signal further controls the pulse width modulator to stop outputting the pulse width modulation signal. At this time, the primary side coil stops operating due to the switching switch stopping its switching operation, so the output voltage of the secondary side coil is dropped by +12V. That is, the voltage supply is currently only supplied from the secondary side coil, so that the output of the secondary side coil When the voltage falls from +12V to +8V (step S303), when the control circuit detects that the output voltage is lower than and reaches +8V by the logic circuit (step S305), the pulse width modulator output pulse wave is again controlled. The width modulation signal, that is, the switching of the switching switch is again activated, and the AC/DC converter is again charged, and the secondary side coil output voltage is returned to +12 V (step S307).

Briefly, the AC/DC converter of the present invention provides a fluctuating output voltage within a specified range when in the standby mode of operation. For example, the output voltage fluctuates from +12 to +8V.

According to the above, since the switching operation of the switching switch continues even in the standby mode due to the circuit configuration of the conventional AC/DC converter, excessive power is lost on the primary side coil. On the contrary, the AC/DC converter provided by the present invention can indirectly control the switching switching stop action of the switching switch in the standby working mode, so that the output voltage from the secondary side coil fluctuates within a specific range, because the switching switch stops. The primary side coil is turned off, so that the coil power loss is zero, and the power consumption of the overall AC/DC converter in the standby mode of operation is also greatly reduced.

It is to be noted that the object of the present invention is to indirectly control the switching of the AC/DC converter in the standby mode so that the output voltage of the AC/DC converter fluctuates within a certain range. However, all the steps of FIG. 3 are only one way of judging, and the present invention is not limited thereto.

In order to increase the protection against the overvoltage of the AC/DC converter, in the preferred embodiment of the present invention, the logic circuit can further compare the digital signal with a third threshold, wherein the third threshold is greater than the The first threshold value, when the digital signal is greater than the third threshold, the control circuit can determine that the AC/DC converter enters an overvoltage mode of operation, and the control circuit outputs a corresponding control signal, thereby controlling the pulse width modulator to stop. Output pulse width modulation signal. That is, the output voltage of the AC/DC converter is continuously increased, and the operation of the primary side coil is turned off, so that the output voltage of the secondary side coil is continuously lowered to achieve circuit protection at the time of overvoltage.

The above description is only an embodiment of the present invention, and is not intended to limit the scope of the invention.

2‧‧‧AC/DC converter

201‧‧‧ Full Bridge Rectifier Filter Circuit

Wp‧‧‧ primary side coil

Ws‧‧‧ secondary coil

SW‧‧‧Toggle switch

203‧‧‧Control circuit

2031‧‧‧ Analog Digital Converter

2033‧‧‧Logical Circuit

2035‧‧‧Digital Analog Converter

2037‧‧‧Standby command setter

205‧‧‧Return circuit

2051‧‧‧Light emitting elements

2053‧‧‧Light detecting component

207‧‧‧ pulse width modulator

PWM‧‧‧ pulse width modulation signal

Claims (11)

An AC/DC converter for reducing standby power consumption, comprising: a primary side coil, a first end of the primary side coil is for receiving an input voltage, and a second end of the primary side coil is connected to a first end a switching switch; a secondary side coil electromagnetically coupling the primary side coil for inducing an output voltage; a control circuit electrically connected to the secondary side coil, the control circuit comprising: an analog to digital converter, Receiving the output voltage and converting into a digital signal; and a logic circuit electrically connected to the analog digital converter, outputting a control signal according to the received digital signal; a feedback circuit electrically coupled to the control a circuit for receiving the control signal, and outputting a feedback signal according to the control signal; and a pulse width modulator electrically connected between the feedback circuit and the switch, the pulse width modulator generating a pulse width modulation signal is used to control the switch, wherein a duty cycle of the pulse width modulation signal is controlled by the feedback signal; and the adjustment is controlled by the feedback The pulse width of the signal modulates the duty cycle of the signal, which in turn controls the output voltage of the AC/DC converter. The AC/DC converter of claim 1, wherein the feedback circuit is an optical coupler, comprising a light emitting component and a light detecting component, wherein the light emitting component is electrically connected to the control circuit, The light detecting component is electrically connected to the pulse width modulator, and the light detecting component is configured to receive the light signal generated by the light emitting component. The AC/DC converter of claim 2, wherein the light emitting element is a light emitting diode, and the light detecting element is one of a photodiode and a photoelectric crystal. The AC/DC converter of claim 3, wherein the feedback signal is a current signal, and the feedback circuit adjusts the magnitude of the output current signal according to the received control signal. The AC/DC converter of claim 1, wherein the switch is a MOSFET, the drain of the MOSFET is connected to the primary side coil, the gold The gate of the oxygen half field effect transistor is coupled to the pulse width modulator for receiving the pulse width modulation signal. The AC/DC converter of claim 1, wherein the control circuit further comprises: a digital analog converter electrically connected between the logic circuit and the feedback circuit for receiving the control signal, And converting the control signal into an analog format output to the feedback circuit. The AC/DC converter of claim 1, wherein the AC/DC converter further comprises: a full bridge rectification filter circuit electrically connected to the first end of the primary side coil for receiving a The mains is converted to the rectified input voltage to be supplied to the primary side coil. The AC/DC converter of claim 1, wherein the control circuit further comprises: a standby command setter electrically connected to the logic circuit for setting whether the AC/DC converter performs a standby operation mode. The AC/DC converter of claim 8, wherein the logic circuit converts the digital signal to a first time when the AC/DC converter performs the standby mode of operation A threshold value and a second threshold value are compared to output a corresponding control signal, and the first threshold value is greater than the second threshold value. The AC/DC converter of claim 9, wherein the control circuit further controls the digital signal when the digital signal is greater than or equal to the first threshold when the AC/DC converter performs the standby mode of operation The pulse width modulator stops outputting the pulse width modulation signal until the digital signal is less than or equal to the second threshold, and the control circuit outputs the corresponding control signal according to the digital signal, thereby adjusting and improving the alternating current/ This output voltage of the DC converter. The AC/DC converter of claim 1, wherein the control circuit determines that the AC/DC converter is entering an overvoltage when the logic circuit compares the digital signal by a third threshold. In the working mode, the control circuit outputs a corresponding control signal, thereby controlling the pulse width modulator to stop outputting the pulse width modulation signal, wherein the third threshold is greater than the first threshold.