WO2022206481A1 - Power conversion circuit and adapter - Google Patents

Abstract

Provided are a power conversion circuit (20) and an adapter (12). The power conversion circuit (20) comprises: a primary circuit (21; 100), comprising a first rectifier filter circuit (101) and a first control chip (102); a secondary circuit (22; 200), comprising a second rectifier filter circuit (201) and a second control chip (202); a transformer (23; 300), comprising a magnetic core (301), a primary winding (302) and a first secondary winding (303); and a first sampling circuit (400), used for collecting output current at a power output end, wherein the first control chip (102) outputs or stops outputting a PWM signal according to the output current; when the power output end is connected to a load, the output current is not continuously zero, and the first control chip (102) outputs a PWM signal to the primary winding (302); and when the power output end is not connected to the load, the output current is continuously zero, and the first control chip (102) stops outputting the PWM signal to the primary winding (302), so as to turn off the secondary circuit (22; 200), the transformer (23; 300), and the circuit of the first control chip (102) used for outputting the PWM signal. The circuit can reduce the standby power consumption of the conversion circuit in a no-load mode and improve the conversion efficiency in a light-load mode.

Description

A power conversion circuit and adapter

This application claims the priority of the Chinese patent application with the application number 202110354837.6 and the application title "A Power Conversion Circuit and Adapter" filed with the State Intellectual Property Office of China on March 31, 2021, the entire contents of which are incorporated herein by reference Applying.

technical field

The present application relates to the field of circuits, and more particularly, to a power conversion circuit and an adapter.

Background technique

It is estimated that the number of smartphones in the world alone will exceed 6 billion in 2020, and other mobile terminal equipment such as computers, the minimum number may exceed 12 billion. All kinds of mobile electronic devices need to use AC-DC power adapters for power supply or energy storage. It can be simply calculated that the number of AC-DC power adapters in the world exceeds 12 billion. The survey found that most people's usage habits are that the power adapter is plugged into the power socket for a long time. According to relevant standards, the standby power consumption threshold of the power adapter is 100mW, that is to say, the power adapter plugged into the power socket is not connected to the terminal equipment ( i.e. no load) will also generate power consumption.

In the load mode, the maximum conversion efficiency of the AC-DC power adapter is generally designed to be between 70% and 90% of the nominal output power. When the output power is less than 70% of the nominal power, as the output power decreases, the power The conversion efficiency also decreases. Therefore, in the case of no-load or light-load output, the conversion efficiency of the conversion circuit of the existing power adapter is low.

SUMMARY OF THE INVENTION

Embodiments of the present application provide a power conversion circuit and an adapter, which can reduce standby power consumption in no-load mode and improve conversion efficiency in light-load mode.

In a first aspect, an embodiment of the present application provides a power conversion circuit, which has a power input terminal and a power output terminal. The power conversion circuit includes: a primary circuit, including a first rectifier and filter circuit and a first control chip, the first A rectifier and filter circuit is connected to the input end of the power supply; the secondary circuit includes a second rectifier filter circuit and a second control chip, the second rectifier filter circuit is connected to the output end of the power supply, and the second control chip uses Adjust the voltage in the second rectifier filter circuit according to the required working voltage and output the adjusted voltage through the power output; the transformer includes a magnetic core, a primary winding and a first secondary winding, the The primary winding is wound on the magnetic core on the side of the primary circuit and is connected to the output end of the first rectifier and filter circuit, and the first secondary winding is wound on the magnetic core on the side of the secondary circuit and connected to the input end of the second rectification filter circuit; the power conversion circuit further includes a first sampling circuit, the first sampling circuit is used to collect the output current at the output end of the power supply, the first sampling circuit A control chip is used to output or stop outputting a PWM signal according to the output current collected by the first sampling circuit, wherein: when the power output terminal is connected to a load, the output current sampled by the first sampling circuit is discontinuous as zero, the first control chip outputs the PWM signal to the primary winding; when the power output is not connected to a load, the output current sampled by the first sampling circuit is continuously zero, and the first The control chip stops outputting the PWM signal to the primary winding, so as to turn off the secondary circuit, the transformer and the circuit of the first control chip for outputting the PWM signal.

In the above solution, when the power output terminal of the power conversion circuit is connected to a load, the output current sampled by the first sampling circuit is discontinuous to zero, and the first control chip can output a PWM signal according to the output current, so that the output terminal of the power conversion circuit can output a PWM signal. The output is suitable for the working voltage of the load, and in the no-load mode, the power output is not connected to the load, and the output current sampled by the first sampling circuit is continuously zero. At this time, the first control chip of the power conversion circuit can stop outputting PWM The signal is sent to the primary winding, that is, the GATE pin of the first control chip turns off the output, and no longer outputs the jump signal, so that the secondary circuit, the transformer and the circuit used for outputting the signal of the first control chip are turned off, thereby reducing the power consumption. The power consumption during load and when the power output terminal of the power conversion circuit is reconnected to the load, the output current sampled by the first sampling circuit is discontinuous to zero, and the first control chip can resume the output PWM signal according to the output current, that is, when the output current is empty The circuit that is turned off during load can be automatically turned on to ensure that it can meet the normal working requirements under the load mode. In addition, the role of the optocoupler device can be replaced by a current sensor. Therefore, the optocoupler device can be removed. Compared with the optocoupler device, the current sensor has a more sensitive response, which makes the control accuracy and real-time performance of the first control chip better.

In a possible implementation manner, the first rectifying and filtering circuit is configured to rectify and filter the AC high voltage power input through the power input terminal to form a DC high voltage power and input it to the primary winding, so The PWM signal output by the first control chip to the primary winding is used to convert the DC high voltage into a high-frequency high-voltage pulse waveform, and the high-frequency high-voltage pulse waveform is converted into a high-frequency high-voltage pulse waveform through the first secondary winding. The high-frequency low-voltage pulse waveform is then output to the second rectifying and filtering circuit, and the second rectifying and filtering circuit is used for rectifying and filtering the high-frequency low-voltage pulse waveform. That is to say, the AC high-voltage power input from the power input terminal can be rectified and filtered through the first rectifier and filter circuit to obtain the DC high-voltage power. Then, the PWM signal can be output through the first control chip, and the high-voltage DC power can be converted into The high-frequency high-voltage pulse waveform can be converted into a high-frequency low-voltage pulse through a transformer, and then the high-frequency low-voltage pulse waveform is rectified and filtered through the second filter and rectifier circuit. The voltage in the rectifier and filter circuit can be adjusted, and the required working voltage can be output from the output terminal of the power supply.

In a possible implementation manner, the first sampling circuit includes a current sensor, the current sensor includes: a Hall chip and a wire, the Hall chip is provided with a plurality of magnetic signal sensing points, and the wire is The middle part is arranged between the plurality of magnetic signal induction points, and the wire is electrically insulated from the plurality of magnetic signal induction points, the power output terminal includes an output positive electrode and an output negative electrode, and the wire is coupled to the Between the positive output terminal of the secondary circuit and the output positive terminal or the wire is coupled between the negative output terminal of the secondary circuit and the output negative terminal, the plurality of magnetic signal induction points are used to connect the The current signal in the wire is converted into a magnetic signal, and the Hall chip is used to convert the magnetic signal into a voltage signal or a digital signal; one end of the communication pin is connected to the Hall chip and the other end is used to communicate with the Hall chip. The first control chip is connected to feed back the voltage signal or the digital signal to the first control chip, so that the first control chip obtains the output current according to the voltage signal or the digital signal. Among them, the "positive output terminal of the secondary circuit" refers to the output terminal of the secondary circuit that is connected to the output positive terminal of the power output terminal of the power conversion circuit, and the "negative output terminal of the secondary circuit" refers to the output terminal of the secondary circuit and the output terminal of the power conversion circuit. The output terminal of the power output terminal of the power conversion circuit is connected to the output negative pole. Since the wires of the current sensor are electrically insulated from the plurality of magnetic signal sensing points, there is no electric shock when the user touches the output end of the power supply, and the use is safer.

In a possible implementation manner, the primary circuit further includes a first power supply circuit, and the first power supply circuit is configured to supply power to the first control chip when the first control chip does not output the PWM signal . Since the first control chip can only rely on the second secondary winding of the transformer for power supply when it outputs the PWM signal, in order to ensure that the first control chip can work normally when the PWM signal is not output, the primary circuit also includes a first power supply circuit to provide power when the first control chip does not output the PWM signal. When the control chip does not output the PWM signal, power is supplied to the first control chip.

In a possible implementation manner, the power input terminal includes an input anode and an input cathode, and the first power supply circuit includes: a first diode coupled between the input anode and the first node; A second diode is coupled between the input cathode and the first node; a first resistor is coupled between the first node and the first control chip.

In a possible implementation manner, the transformer further includes a second secondary winding, the primary circuit further includes a second power supply circuit, and the second secondary winding is wound around the magnetic core on the primary circuit side on top of and spaced apart from the primary winding, the second secondary winding is used to convert the high-frequency high-voltage pulse waveform into a high-frequency low-voltage pulse waveform, and the second power supply circuit is used for the first control chip. When outputting the PWM signal, the high-frequency low-voltage pulse waveform in the second secondary winding is converted into an output voltage, and the output voltage is a DC voltage suitable for supplying power to the first control chip. In this way, when the first control chip outputs the PWM signal, it can rely on the second secondary winding of the transformer to supply power. Compared with using the first power supply circuit to supply power, the loss of the circuit is smaller at this time.

In a possible implementation manner, the second power supply circuit includes: a third rectifier and filter circuit, and the third rectifier and filter circuit is used to convert the high-frequency low-voltage pulse waveform in the second secondary winding into DC voltage; a voltage dividing filter circuit for filtering and dividing the DC voltage to generate the output voltage. That is to say, when the first control chip outputs the PWM signal, it cannot directly use the high-frequency low-voltage pulse waveform in the second secondary winding for power supply. Only the voltage filter circuit can generate an output voltage suitable for supplying power to the first control chip.

In a possible implementation manner, the third rectifying filter circuit includes: a first capacitor, one end of which is grounded; a third diode, a cathode of the third diode is connected to the first capacitor The other end of a capacitor is connected, the anode of the third diode is connected to one end of the second secondary winding, and the other end of the second secondary winding is grounded.

In a possible implementation manner, the voltage dividing filter circuit includes: a second resistor, the second resistor is coupled between one end of the second secondary winding and the second node; a third resistor, the One end of the third resistor is grounded, and the other end is connected to the second node; for the second capacitor, one end of the second capacitor is grounded, and the other end is connected to the second node and the first control chip in sequence.

In a possible implementation manner, the power conversion circuit further includes a second sampling circuit, configured to sample the current and voltage output by the first rectification and filtering circuit to obtain the primary input power, and the first control chip according to The ratio of the output current to the primary input power adjusts the frequency of the PWM waveform. That is to say, a current sensor is connected in series on the output channel of the power conversion circuit, the secondary output current can be obtained through the current sensor, and the primary input power can be obtained by sampling the current and voltage output by the first rectification filter circuit through the second sampling circuit, According to the relationship between the ratio of the secondary output current and the primary input power obtained in real time and the set threshold value, the real-time output current value detected by the current sensor can dynamically adjust the frequency of the PWM waveform. On the premise of ensuring that the output voltage of the output channel of the power conversion circuit meets the working requirements, by reducing the frequency of the PWM waveform, the switching transistors (such as the MOSFET connected to the GATE pin of the first control chip) and the power conversion circuit can be reduced. The dynamic loss of the diode and the core loss of the transformer can improve the conversion efficiency at light load conditions. In addition, the PSM circuit and the EMI circuit can be eliminated, and the circuit structure can be simplified.

In a possible implementation manner, the first control chip is configured to: acquire a first ratio of the output current to the primary input power, and when it is determined that the first ratio is less than a set threshold, set the The frequency of the PWM waveform is adjusted downward by the first set value, and the second ratio of the output current to the primary input power is obtained again; when it is determined that the second ratio is greater than the first ratio, the PWM waveform is The frequency of the PWM waveform continues to adjust the first set value downward; when it is determined that the second ratio is smaller than the first ratio, the frequency of the PWM waveform is adjusted upward to the second set value, and the second set value is The value is smaller than the first set value; after adjustment, the ratio of the output current to the primary input power is maximized. That is to say, when it is determined that the output power of the power conversion circuit is small, the ratio of the output current to the primary input power (the first ratio) can be obtained, and then the frequency of the PWM waveform is reduced by the first set value once to obtain the adjusted frequency The ratio of the output current to the primary input power (the second ratio), if the second ratio is greater than the first ratio, it means that the frequency can continue to be reduced; if the second ratio is less than the first ratio, it means that the adjustment is too large, that is, the maximum ratio is at Between the first ratio and the second ratio, at this time, the second set value (less than the first set value) can be recalled, and after adjustment, the frequency of the PWM waveform at the maximum ratio can be determined.

In a possible implementation manner, the second set value is the first set value/N ^m , N is a positive integer, and N≥2, m is the number of consecutive callbacks, and m is a positive integer , and m≥1. That is to say, if there are consecutive callbacks, the value of each callback will be one-Nth of the previous callback value. For example, assuming N=2, the first setting value is Δf, the second setting value is Δf/N ^m =Δf/2 ^m , when the output power is lower than 90% of the nominal value, the secondary output is obtained The ratio of current to primary input power, adjust the PWM waveform frequency downward by Δf, and then obtain the ratio of secondary output current and primary input power. If the current ratio is greater than the previous ratio, continue to adjust Δf downward. If the current ratio is smaller than the previous ratio, Then adjust upward by Δf/2; then obtain the ratio of secondary output current and primary input power, if the current ratio is still smaller than the previous ratio, then adjust upward by Δf/4; if the current ratio is greater than the previous ratio, then adjust downward by Δf/4 ; After gradual adjustment, the ratio of secondary output current to primary input power is maximized.

In a possible implementation manner, the first rectifying and filtering circuit includes: a first filtering circuit for filtering out noise in the AC high-voltage power input through the power input terminal; a first rectifying circuit for filtering The second filter circuit is used to filter the noise in the DC high voltage and filter the noise from the DC high voltage. output to the primary winding; the second sampling circuit includes a sampling resistor, the sampling resistor is connected in series between the positive output terminal of the first rectifier circuit and the positive output terminal of the second filter circuit, the first A control chip is connected to both ends of the sampling resistor to collect the voltage at both ends of the sampling resistor, and obtain the primary input power according to the voltage difference between the two ends of the sampling resistor and the resistance of the sampling resistor . That is to say, a sampling resistor is connected in series in the primary circuit, and the primary input power can be obtained through the sampling resistor. Assuming that the resistance of the sampling resistor is r, the first side of the sampling resistor is connected to the positive output terminal of the first rectifier circuit, and the sampling The voltage of the first side of the resistor is U1, the second side of the sampling resistor is connected to the positive output terminal of the second filter circuit, the voltage of the second side of the sampling resistor is U2, and the primary input power Pin=U1(U1-U2)/ r, U1 is greater than U2.

In a possible implementation manner, the second filter circuit includes: a third capacitor, the negative electrode of the third capacitor is grounded, and the positive electrode of the third capacitor is connected to the positive output end of the first rectifier circuit, The negative output end of the first rectifier circuit is grounded; the fourth capacitor, the negative electrode of the fourth capacitor is connected to one end of the primary winding, and the positive electrode of the fourth capacitor is connected to the other end of the primary winding; The sampling resistor is coupled between the positive electrode of the third capacitor and the positive electrode of the fourth capacitor.

In a possible implementation manner, the second rectifying and filtering circuit includes: a second rectifying circuit, connected to the first secondary winding, for converting the high-frequency low-voltage pulse waveform in the first secondary winding Converted to a direct current voltage; a third filter circuit is used to filter the direct current voltage and output it through the power supply output terminal.

In a second aspect, an embodiment of the present application provides an adapter, where the adapter includes the power conversion circuit provided in the first aspect.

The power conversion circuit and the adapter of the embodiments of the present application can reduce the standby power consumption in the no-load mode and improve the conversion efficiency in the light-load mode. Specifically, in the no-load mode, the secondary circuit, the transformer and part of the primary circuit (such as the circuit of the first control chip for outputting the PWM signal) can be turned off, thereby reducing the power consumption at no-load, and reconnecting the When the electrical equipment (load) is turned on, it can automatically restore the opening of the relevant circuits to ensure that the normal working requirements can be met under the load mode; under the light load, the frequency of the PWM waveform can be adjusted, which broadens the load range of the high-efficiency charging of the power supply. It can also maintain a high conversion efficiency under load, which reduces the overall power consumption of the system and contributes to energy conservation and emission reduction.

Description of drawings

FIG. 1 is a schematic diagram of an application scenario of an adapter provided by an embodiment of the present application;

2 is a schematic structural diagram of a power conversion circuit of the adapter in FIG. 1;

3 is a schematic structural diagram of a power conversion circuit provided by the first embodiment of the present application;

4 is a schematic structural diagram of a current sensor in the power conversion circuit of FIG. 3;

FIG. 5 is a schematic structural diagram of a power conversion circuit provided by a second embodiment of the present application.

Detailed ways

The technical solutions in the embodiments of the present invention will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some of the embodiments of the present specification, but not all of the embodiments.

In the description of this specification, "one embodiment" or "some embodiments" etc. means that a particular feature, structure or characteristic described in connection with the embodiment is included in one or more embodiments of this specification. Thus, appearances of the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in other embodiments," etc. in various places in this specification are not necessarily All refer to the same embodiment, but mean "one or more but not all embodiments" unless specifically emphasized otherwise.

Wherein, in the description of this specification, unless otherwise stated, "/" means or means, for example, A/B can mean A or B; "and/or" in this document is only an association to describe the associated object Relation, it means that there can be three kinds of relations, for example, A and/or B can mean that A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present application, "plurality" refers to two or more than two.

In the description of this specification, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implying the number of indicated technical features. Thus, a feature defined as "first" or "second" may expressly or implicitly include one or more of that feature. The terms "including", "including", "having" and their variants mean "including but not limited to" unless specifically emphasized otherwise.

It can be understood that, various numbers and numbers involved in the embodiments of the present application are only for the convenience of description, and are not used to limit the scope of the embodiments of the present application.

FIG. 1 is a schematic diagram of an application scenario of an adapter provided by an embodiment of the present application. As shown in FIG. 1 , the application scenario includes an external power supply 11 , an adapter 12 and a device to be charged 13 . The external power source 11 may be AC commercial power, and the device to be charged 13 may include a mobile phone, a notebook computer, a battery, or the like, which is not limited in this embodiment of the present application. Normally, the adapter 12 can be connected to the external power source 11, and the adapter 12 includes a power conversion circuit, which is used to convert the higher voltage provided by the external power source 11 into a lower voltage that meets the charging or power supply standard of the device to be charged 13, And charge or supply power to the device 13 to be charged.

Under the load mode, the maximum conversion efficiency of the AC-DC power adapter is generally designed to be between 70% and 90% of the nominal output power. When the output power is less than 70% of the nominal power, as the output power decreases, the power The conversion efficiency also decreases; when the device is idle or dormant, the load of the AC-DC power conversion circuit is very light, usually below 10% of the nominal output power of the power supply, making the AC-DC power conversion circuit itself a reduction in the overall system. power consumption bottleneck. The conversion efficiency design of the current AC-DC power conversion circuit under load mode is very mature. Therefore, improving the conversion efficiency of the AC-DC power conversion circuit under no-load and light load is the key development direction of energy conservation and emission reduction.

FIG. 2 is a schematic structural diagram of a power conversion circuit of the adapter in FIG. 1 . As shown in FIG. 2 , the power conversion circuit 20 generally includes a primary circuit 21 , a secondary circuit 22 and a transformer 23 . The secondary circuit 21 is connected to the primary winding of the transformer 23 , and the secondary circuit 22 is connected to the secondary winding of the transformer 23 . The primary circuit may include a PWM control chip, the secondary circuit may include a protocol control chip, and an optocoupler device (not shown in the figure) is connected between the PWM control chip and the protocol control chip. The optocoupler device may include a transmitting part and a receiving part, the transmitting part is connected with the protocol control chip, and the receiving part is connected with the PWM control chip.

Among them, in the no-load mode (that is, the output terminal of the secondary circuit is not connected to the load), the same as the load mode, the size of the output current is roughly fed back through the optocoupler device, and the PWM control chip adjusts the PWM pulse waveform according to the output current. It is ensured that the output power of the power conversion circuit can meet the working requirements and the conversion efficiency is relatively high. Specifically, when the output current becomes larger, the light output by the transmitting part becomes weaker, and the value of the optical signal converted into an electrical signal by the receiving part becomes correspondingly smaller. The PWM control chip increases the duty cycle of the output PWM signal according to the weakened signal. ; When the output current becomes smaller, the light output by the transmitting part becomes stronger, and the value of the receiving part converting the optical signal into an electrical signal becomes correspondingly larger, and the PWM control chip reduces the duty cycle of the output PWM signal according to the larger signal.

The above-mentioned power conversion circuit cannot realize the shutdown and wake-up functions of the secondary circuit in the no-load mode, that is, the secondary circuit is still in the connected state in the no-load mode, resulting in high base power consumption of the circuit. Specifically, according to the relevant power consumption requirements, for example, for a power adapter below 50W, the no-load power consumption can be 100mW; for a power adapter from 50W to 250W, the no-load power consumption can be 210mW. If the circuit design of the power adapter can be optimized in order to reduce the standby power consumption of the power adapter, the benefits of energy saving and emission reduction in the world are very considerable.

In addition, the above-mentioned power conversion circuit improves the efficiency of light load by using the pulse frequency hopping mode (also known as pulse step modulation, PSM) in the light load mode; When the load and the output power of the output end of the power conversion circuit are within the setting range of 70% to 90% of the nominal power), the AC/DC power swivel circuit works in the pulse width modulation (Pulse Width Modulation, PWM) mode. At light load, the working mode of the AC/DC power swivel circuit is converted from PWM mode to PSM mode, which can switch the dual-tube operation to single-tube operation, thereby improving the conversion efficiency under light load. However, the PSM mode will generate ultra-wide-band noise, which increases the difficulty of electromagnetic interference (Electro Magnetic Interference, EMI) filtering. In order to meet the requirements of the EMI standard, an EMI circuit needs to be added.

That is to say, in the case of no-load or light-load output of the above solution, the conversion efficiency of the AC-DC conversion circuit is low.

In view of this, embodiments of the present application provide a power conversion circuit and an adapter including the power conversion circuit, which can reduce standby power consumption in no-load mode and improve conversion efficiency in light-load mode. Specifically, in the no-load mode, the secondary circuit, the transformer and part of the primary circuit (such as the circuit of the first control chip for outputting the PWM signal) can be turned off, thereby reducing the power consumption at no-load, and reconnecting the When the power supply is turned on, the related circuits can be automatically restored to ensure that the normal working requirements can be met under the load mode; under the light load, the frequency of the PWM waveform can be adjusted, which broadens the load range of the high-efficiency charging of the power supply. It can maintain a high conversion efficiency, reduce the overall power consumption of the system, and contribute to energy conservation and emission reduction. For example, only reducing the standby power consumption of the mobile phone power adapter to less than 20mW, it is conservatively estimated that the world can reduce the power consumption of 800 million kilowatt-hours a year. Since the no-load power consumption of the high-power power adapter is higher, the technical solution can also be applied to the high-power power adapter, which brings more considerable benefits.

FIG. 3 is a schematic diagram of a specific structure of the power conversion circuit provided by the first embodiment of the present application. As shown in FIG. 3 , the power conversion circuit has a power input terminal and a power output terminal. The power input terminal includes an input positive pole P1 and an input negative pole P2, and the power output terminal includes an output positive pole Q1/VOUT and an output negative pole Q2/GND. The power conversion circuit includes a primary circuit 100 , a secondary circuit 200 and a transformer 300 . The primary circuit 100 includes a first rectifying and filtering circuit 101 and a first control chip 102. The first rectifying and filtering circuit 101 is connected to a power input terminal, that is, an input positive electrode P1 and an input negative electrode P2. The secondary circuit 200 includes a second rectifier and filter circuit 201 and a second control chip 202. The second rectifier and filter circuit 201 is connected to the output terminal of the power supply, that is, the output positive electrode Q1 and the output negative electrode Q2. The second control chip 202 is used to operate according to the required operating voltage. The voltage in the second rectifying and filtering circuit 201 is adjusted and the adjusted voltage is output through the output terminal of the power supply, that is, the output positive electrode Q1 and the output negative electrode Q2. The transformer 300 includes a magnetic core 301, a primary winding 302 and a first secondary winding 303. The primary winding 302 is wound on the magnetic core 301 on the side of the primary circuit 100 and is connected to the output end of the first rectifier and filter circuit 101. The first secondary The winding 303 is wound on the magnetic core 301 on the side of the secondary circuit 200 and is connected to the input end of the second rectifying and filtering circuit 201 .

The first rectifying and filtering circuit 101 is used for rectifying and filtering the AC high voltage power input through the power input terminal, that is, the input positive electrode P1 and the input negative electrode P2, to form a DC high voltage power and input it to the primary winding 302. The first control chip 102 The PWM signal output to the primary winding 302 is used to convert the DC high voltage into a high frequency high voltage pulse waveform, and the high frequency high voltage pulse waveform is converted into a high frequency low voltage pulse waveform through the first secondary winding 303 and then output to the second The rectifying and filtering circuit 201 and the second rectifying and filtering circuit 201 are used for rectifying and filtering the high-frequency low-voltage pulse waveform.

Further, the first rectifying and filtering circuit 101 may include a first filtering circuit 1011 , a first rectifying circuit 1012 and a second filtering circuit 1013 . The first filter circuit 1011 is used for filtering out the noise in the AC high voltage power input through the power input terminal, that is, the input positive electrode P1 and the input negative electrode P2. The first rectifier circuit 1012 is used for converting the AC high voltage power after noise filtering into the DC high voltage power. The second filter circuit 1013 is used for filtering the noise in the DC high voltage power and outputting the DC high voltage power after filtering the noise to the primary winding 302 . Also, the second filter circuit 1013 may include a third capacitor C3 and a fourth capacitor C4. The negative electrode of the third capacitor C3 is grounded, the positive electrode of the third capacitor C3 is connected to the positive output terminal of the first rectifier circuit 1012 , and the negative output terminal of the first rectifier circuit 1012 is grounded. The negative electrode of the fourth capacitor C4 is connected to one end of the primary winding 302, and the positive electrode of the fourth capacitor C4 is connected to the other end of the primary winding 302. That is to say, after the alternating current mains AC enters the power conversion circuit of the adapter, it reaches the transformer 300 through the first filter circuit 1011 , the full-bridge rectifier circuit 1012 and the second filter circuit 1013 . Among them, the filter circuit is used to filter out noise, and the full-bridge rectifier circuit is used to convert AC high voltage into DC high voltage. The first control chip 102, such as a PWM control chip, can convert high-voltage direct current into a high-frequency pulse waveform, and then convert it into a low-voltage pulse waveform by the transformer 300, and then cooperate with the post-stage rectifier circuit 201 and the second control chip 202, such as a protocol control chip, to realize low-voltage. DC output.

Also, the second rectifying and filtering circuit 201 may include a second rectifying circuit 2011 and a third filtering circuit 2012 . The second rectifier circuit 2011 is connected to the first secondary winding 303 for converting the high frequency low voltage pulse waveform in the first secondary winding 303 into a DC voltage. The third filter circuit 2012 is used to filter the DC voltage and output it through the power output terminals Q1 and Q2.

As shown in FIG. 3 , the primary circuit 100 further includes a first power supply circuit, and the first power supply circuit is configured to supply power to the first control chip 102 when the first control chip 102 does not output a PWM signal. Specifically, the first power supply circuit includes a first diode D1, a second diode D2 and a first resistor R1. The first diode D1 is coupled between the input anode P1 and the first node N1. The second diode D2 is coupled between the input cathode P2 and the first node N1. The first resistor R1 is coupled between the first node N1 and the first control chip 102 .

In addition, the transformer 300 further includes a second secondary winding 304, the primary circuit 100 further includes a second power supply circuit, the second secondary winding 304 is wound on the magnetic core 301 on the side of the primary circuit 100 and is spaced from the primary winding 302, and the second The secondary winding 304 is used to convert the high-frequency high-voltage pulse waveform into a high-frequency low-voltage pulse waveform, and the second power supply circuit is used to convert the high-frequency low-voltage pulse waveform in the second secondary winding 304 when the first control chip 102 outputs the PWM signal. The output voltage is converted into an output voltage, and the output voltage is a DC voltage suitable for supplying power to the first control chip 102 . That is to say, when the first control chip 102 does not output the PWM signal, the first control chip 102 is powered by the first power supply circuit; when the first control chip 102 outputs the PWM signal, the first control chip 102 is powered by the second power supply circuit, namely the transformer 300 The second secondary winding 304 is powered.

Specifically, the second power supply circuit may include a third rectification filter circuit and a voltage divider filter circuit. The third rectifying filter circuit is used to convert the high frequency low voltage pulse waveform in the second secondary winding 304 into a DC voltage. The voltage divider filter circuit is used to filter and divide the DC voltage to generate the output voltage. Wherein, the third rectifying filter circuit includes a first capacitor C1 and a third diode D3. One end of the first capacitor C1 is grounded. The cathode of the third diode D3 is connected to the other end of the first capacitor C1, the anode of the third diode D3 is connected to one end of the second secondary winding 304, and the other end of the second secondary winding 304 is grounded. The voltage dividing filter circuit includes a second resistor R2, a third resistor R3 and a second capacitor C2. The second resistor R2 is coupled between one end of the second secondary winding 304 and the second node N2. One end of the third resistor R3 is grounded, and the other end is connected to the second node N2. One end of the second capacitor C2 is grounded, and the other end is connected to the second node N2 and the first control chip 102 in sequence.

Continuing to refer to FIG. 3 , the power conversion circuit further includes a first sampling circuit 400. The first sampling circuit 400 is used to collect the output current at the output terminal of the power supply, that is, the output positive Q1 or the output negative Q2. The output current collected by the sampling circuit 400 outputs or stops outputting a PWM signal, wherein the first sampling circuit 400 may include a current sensor S, and the PWM signal is output to the primary winding 302 through a switch MOSFET connected to the GATE terminal of the first control chip 102 . When a load is connected to the output terminal of the power supply, that is, the positive output Q1 and the negative output Q2 , the output current sampled by the first sampling circuit 400 is discontinuously zero, and the first control chip 102 outputs a PWM signal to the primary winding 302 . When the output terminal of the power supply, that is, the positive output Q1 and the negative output Q2 are not connected to the load, the output current sampled by the first sampling circuit 400 is continuously zero, and the first control chip 102 stops outputting the PWM signal to the primary winding 302 to turn off the secondary circuit 200 , the transformer 300 and the circuit of the first control chip 102 for outputting the PWM signal.

That is to say, when a load is connected to the power output end of the power conversion circuit, the output current sampled by the first sampling circuit 400 is discontinuous to zero, and the first control chip 102 can output a PWM signal according to the output current, so that the output current of the power conversion circuit is The output terminal outputs a working voltage suitable for the load, and in the no-load mode, the output terminal of the power supply is not connected to the load, and the output current sampled by the first sampling circuit 400 is continuously zero. At this time, the first control chip 102 of the power conversion circuit It can stop outputting the PWM signal to the primary winding 302, that is, the GATE pin of the first control chip 102 turns off the output, and no longer outputs the jump signal, so that the secondary circuit 200, the transformer 300 and the first control chip 102 are used to output the PWM signal. The circuit is turned off, thereby reducing the power consumption at no-load, and when the power output terminal of the power conversion circuit is reconnected to the load, the output current sampled by the first sampling circuit 400 is discontinuous to zero, and the first control chip 102 can According to the output current, the output PWM signal is restored, that is, the circuit that is turned off at no-load can be automatically restored to be turned on, so as to ensure that the normal working requirements can be met in the loaded mode.

FIG. 4 is a schematic structural diagram of the current sensor S in the power conversion circuit of FIG. 3 . As shown in FIG. 4 , the current sensor S includes a hall chip S1 , a wire S2 and a communication pin. The Hall chip S1 is provided with a plurality of magnetic signal induction points, the middle part of the wire S2 is arranged between the plurality of magnetic signal induction points, and the wire S2 is electrically insulated from the plurality of magnetic signal induction points, and the wire S2 is coupled to the secondary The positive output terminal of the circuit 200 and the output positive terminal Q1 or the wire S2 is coupled between the negative output terminal of the secondary circuit 200 and the output negative terminal Q2. That is to say, one end of the wire S2 is the current input pin, the other end of the wire S2 is the current output pin, and the current input pin and the current output pin of the wire S2 are connected in series with the output positive pole in the output end of the power conversion circuit Q1 or output negative terminal Q2. As shown in FIG. 3 , the current input pin and the current output pin of the wire S2 are connected in series at the output negative electrode Q2 of the power conversion circuit.

The “positive output terminal of the secondary circuit 200” refers to the output terminal of the secondary circuit 200 connected to the output positive terminal Q1 in the power output terminal of the power conversion circuit, and the “negative output terminal of the secondary circuit 200” refers to the secondary circuit 200. The output terminal of the stage circuit 200 is connected to the output negative terminal Q2 in the power output terminal of the power conversion circuit. Since the wire S2 of the current sensor S is electrically insulated from the plurality of magnetic signal sensing points, no electric shock will occur when the user touches the output end of the power supply, and the use is safer.

The plurality of magnetic signal sensing points are used to convert the current signal in the wire S2 into a magnetic signal, and the Hall chip S1 is used to convert the magnetic signal into a voltage signal or a digital signal. One end of the communication pin S3 is connected to the Hall chip S1 and the other end is connected to the first control chip 102 to feed back a voltage signal or a digital signal to the first control chip 102, so that the first control chip 102 can respond to the voltage signal or digital signal. get the output current.

Also, the current sensor S may include a plurality of communication pins. In addition, the current sensor S may further include a power supply pin, a grounding pin and a casing S3, the power supply pin is used for connecting with the power supply to supply power to the Hall chip S1, and the grounding pin is used for grounding. Current input pins, current output pins, power supply pins, ground pins, and communication pins are set out of the casing S3.

As shown in FIG. 3 and FIG. 4 , in the power conversion circuit of the first embodiment of the present application, a current sensor S is connected in series to the output channel of the power conversion circuit, and the first control chip 102 detects the current value according to the current value of the current sensor S. Perform circuit control. Specifically, after the mobile phone or other electrical equipment is unplugged from the output end of the power conversion circuit, the current on the output channel connected to the output end is continuously zero, and the current value fed back by the current sensor S to the first control chip 102 is continuously zero. signal, after receiving the signal, the first control chip 102 turns off the PWM waveform output, that is, the GATE pin of the first control chip 102 turns off the output, and no longer outputs the jump signal, so that the secondary circuit 200, the transformer 300 and the The devices in the circuit for outputting the PWM signal of the first control chip 102 are all in a power-off state. At this time, the no-load power consumption of the power conversion circuit is part of the circuits in the primary circuit, such as the first filter circuit 1101 and the first rectifier circuit. 1102 , the power consumption of the first power supply circuit and some circuits of the first control chip 102, etc., thereby reducing the loss of the circuit. When the output end of the power conversion circuit is reconnected to the electrical equipment, a disturbance current/inrush current will be generated on the current sensor S. After receiving the disturbance current/inrush current signal, the first control chip 102 turns on the PWM waveform output of the primary circuit, The circuit is in a normal working state, until the current sensor S continuously detects that the output current is zero again, the PWM waveform output is turned off. In addition, the role of the optocoupler device can be replaced by the current sensor S. Therefore, the optocoupler device can be removed. Compared with the optocoupler device, the current sensor S is more responsive, so that the control accuracy and real-time performance of the first control chip 102 are better.

FIG. 5 is a schematic diagram of a specific structure of a power conversion circuit provided by a second embodiment of the present application. As shown in FIG. 5 , the difference from the power conversion circuit of the first embodiment shown in FIG. 4 is that the power conversion circuit of the second embodiment of the present application further includes a second sampling circuit 500 for sampling the first rectifier The current and voltage output by the filter circuit 101 are used to obtain the primary input power, and the first control chip 102 adjusts the frequency of the PWM waveform according to the ratio of the output current to the primary input power.

The second sampling circuit 400 includes a sampling resistor R, which is connected in series between the positive output end of the first rectifier circuit 1012 and the positive output end of the second filter circuit 1013 , and the first control chip 102 and the sampling resistor R are connected in series. The terminals are connected to collect the voltage at both ends of the sampling resistor R, and the primary input power is obtained according to the voltage difference at both ends of the sampling resistor R and the resistance of the sampling resistor R. Further, the second filter circuit 1013 may include a third capacitor C3 and a fourth capacitor C4. The negative electrode of the third capacitor C3 is grounded, the positive electrode of the third capacitor C3 is connected to the positive output terminal of the first rectifier circuit 1012 , and the negative output terminal of the first rectifier circuit 1012 is grounded. The negative electrode of the fourth capacitor C4 is connected to one end of the primary winding 302 , and the positive electrode of the fourth capacitor C4 is connected to the other end of the primary winding 302 . The sampling resistor R is coupled between the positive electrode of the third capacitor C3 and the positive electrode of the fourth capacitor C4.

Assuming that the resistance value of the sampling resistor R is r, the first side of the sampling resistor R is connected to the positive output terminal of the first rectifier circuit 1012, the voltage of the first side of the sampling resistor R is U1, and the second side of the sampling resistor R is connected to the first side of the sampling resistor R. The positive output terminals of the two filter circuits 1013 are connected, the voltage on the second side of the sampling resistor R is U2, and the primary input power Pin=U1×(U1-U2)/r, where U1 is greater than U2.

Specifically, after the magnetic core 301 of the transformer 300 is selected, the following relationship exists between the PWM wave frequency of the AC-DC power conversion circuit and the output power:

Po=K×F×Ae×Ac(W), where Po is the output power, K is the circuit coefficient, F is the PWM wave frequency, Ae is the cross-sectional area of the magnetic core, and Ac is the window area of the magnetic core.

It can be seen from the formula that for a fixed magnetic core, the higher the frequency of the PWM waveform, the higher the maximum power that can be output; on the contrary, for a certain output power, the volume of the magnetic core can be reduced by increasing the frequency of the PWM waveform.

Also, for a fixed core, the higher the frequency of the PWM waveform, the greater the core loss. Also, the dynamic losses of MOSFETs and diodes are proportional to the PWM wave frequency.

That is to say, for the same power conversion circuit (that is, the magnetic core 301 of the transformer 300 is fixed), the output power of the power conversion circuit can be increased by increasing the frequency of the PWM waveform, but the higher the frequency of the PWM waveform, the loss of the magnetic core, MOSFET and The greater the dynamic loss of the diode. In order to maximize the ratio of the output current to the primary input power, it can be achieved by adjusting the frequency of the PWM multiple times.

Specifically, the first control chip 102 is configured to: obtain a first ratio of the output current to the primary input power, and when it is determined that the first ratio is less than a set threshold, adjust the frequency of the PWM waveform down to the first set value, and obtain again The second ratio of the output current to the primary input power; when it is determined that the second ratio is greater than the first ratio, the frequency of the PWM waveform continues to be adjusted downward to the first set value; when it is determined that the second ratio is smaller than the first ratio, the PWM The frequency of the waveform is adjusted upward to the second set value, and the second set value is smaller than the first set value; after adjustment, the ratio of the output current to the primary input power is maximized.

Wherein, the second set value is the first set threshold/N ^m , N is a positive integer, and N≥2, m is the number of consecutive callbacks, m is a positive integer, and m≥1, that is, continuous When a callback is made, the value of each callback is N times the value of the previous callback. For example, assuming N=2, the first set value is Δf, the second set value is Δf/N ^m , when the output power is lower than 90% of the nominal value, the secondary output current and primary input are obtained Power ratio, adjust the PWM waveform frequency downward by Δf, and then obtain the ratio of secondary output current and primary input power. If the current ratio is greater than the previous ratio, continue to adjust Δf downward. If the current ratio is smaller than the previous ratio, then adjust Δf upward. /2, and then obtain the ratio of the secondary output current to the primary input power. If the current ratio is smaller than the previous ratio, it will be adjusted upward by Δf/4; if the current ratio is greater than the previous ratio, it will be adjusted downward by Δf/4; after gradual adjustment, Maximize the ratio of secondary output current to primary input power.

As shown in FIG. 5 , in the power conversion circuit of the second embodiment of the present application, a current sensor S is connected in series to the output channel of the power conversion circuit, and a sampling resistor R is connected in series in the primary circuit. For the secondary output current, the primary input power can be obtained through the sampling resistor R, and the frequency of the PWM waveform can be dynamically adjusted according to the ratio of the secondary output current and the primary input power obtained in real time. When the output power is more than 90% of the nominal value, the PWM waveform frequency can control the switch tube such as the MOSFET connected to the GATE pin of the first control chip 102 according to the designed maximum value. When the load is light, on the premise of ensuring that the output voltage of the output channel of the power conversion circuit meets the working requirements, by reducing the frequency of the PWM waveform, the dynamic loss of the MOSFET and diode and the core loss of the transformer can be reduced, thereby improving the light load state. conversion efficiency when. In addition, the PSM circuit and the EMI circuit can be eliminated, and the circuit structure can be simplified.

To sum up, by adding a current sensor to the output end of the AC-DC power conversion circuit, the working state of the power conversion circuit is obtained, and when the power conversion circuit is no-load, the secondary circuit and the transformer of the power conversion circuit and the first control circuit are turned off. Part of the circuit of the chip, so as to realize the extremely low power consumption of no-load power conversion; when reconnecting the electrical equipment, the disturbance current detected by the current sensor realizes the automatic opening of the circuit, so as to meet the public's usage habits. The ultra-low no-load power consumption of the power adapter can contribute to the overall energy saving and emission reduction, constitute the super selling point of the product, and enhance the market competitiveness of the product. By adding a current sensor at the output end of the AC-DC conversion circuit to sample the output current, adding a sampling resistor in the primary circuit to obtain the input power by sampling the current and voltage, a closed-loop feedback system is formed, according to the ratio of the output current to the input power , At light load, the PWM waveform frequency can be adjusted in real time, which can broaden the load range of high-efficiency conversion of the power supply, and improve the conversion efficiency of the power conversion circuit at light load, that is, the power supply can maintain a high conversion efficiency under light load, so as to achieve Reduce the overall power consumption of the system and contribute to energy conservation and emission reduction.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention. should be included within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (11)

1. A power conversion circuit, having a power input end and a power output end, is characterized in that, comprising:

   The primary circuit includes a first rectification and filter circuit and a first control chip, and the first rectifier and filter circuit is connected to the power input end;

   The secondary circuit includes a second rectifier and filter circuit and a second control chip, the second rectifier and filter circuit is connected to the output end of the power supply, and the second control chip is used for rectifying the second rectifier according to the required working voltage The voltage in the filter circuit is adjusted and the adjusted voltage is output through the power output;

   A transformer includes a magnetic core, a primary winding and a first secondary winding, the primary winding is wound on the magnetic core on the side of the primary circuit, and is connected to the output end of the first rectifier and filter circuit, the first The primary winding is wound on the magnetic core at the side of the secondary circuit, and is connected to the input end of the second rectifying and filtering circuit;

   The first rectifier and filter circuit is used to rectify and filter the AC high voltage power input through the power input terminal to form a DC high voltage power and input it to the primary winding, and the first control chip is used to output PWM signal to the primary winding, the PWM signal is used to convert the DC high voltage into a high frequency high voltage pulse waveform, and convert the high frequency high voltage pulse waveform into a high frequency low voltage through the first secondary winding The pulse waveform is output to the second rectification and filter circuit, and the second rectification and filter circuit is used for rectifying and filtering the high-frequency low-voltage pulse waveform;

   The power conversion circuit further includes a first sampling circuit, the first sampling circuit is used for collecting the output current at the output end of the power supply, and the first control chip is used for collecting the output current according to the first sampling circuit Output or stop outputting the PWM signal, wherein: when the power output terminal is connected to the load, the first control chip outputs the PWM signal to the primary winding; when the power output terminal is not connected to the load, the The first control chip stops outputting the PWM signal to the primary winding, so as to turn off the secondary circuit, the transformer and the circuit of the first control chip for outputting the PWM signal.
2. The power conversion circuit according to claim 1, wherein the first sampling circuit comprises a current sensor, and the current sensor comprises:

   A Hall chip and a wire, the Hall chip is provided with a plurality of magnetic signal induction points, the middle part of the wire is arranged between the plurality of magnetic signal induction points, and the wire is connected to the plurality of magnetic signal induction points. The signal sensing point is electrically insulated, the power output terminal includes an output positive pole and an output negative pole, the wire is coupled between the positive output terminal of the secondary circuit and the output positive pole or the wire is coupled to the secondary Between the negative output terminal of the circuit and the negative output terminal, the plurality of magnetic signal sensing points are used to convert the current signal in the wire into a magnetic signal, and the Hall chip is used to convert the magnetic signal into a magnetic signal. Voltage signal or digital signal;

   A communication pin, one end is connected to the Hall chip and the other end is used to connect to the first control chip, so as to feed back the voltage signal or the digital signal to the first control chip, so that the first control chip The control chip obtains the output current according to the voltage signal or the digital signal.
3. The power conversion circuit according to claim 1 or 2, wherein the primary circuit further comprises a first power supply circuit, and the first power supply circuit is used for when the first control chip does not output the PWM signal supplying power to the first control chip.
4. The power conversion circuit according to any one of claims 1-3, wherein the transformer further comprises a second secondary winding, the primary circuit further comprises a second power supply circuit, and the second secondary winding Winding on the magnetic core on the primary circuit side and spaced apart from the primary winding, the second secondary winding is used to convert the high-frequency high-voltage pulse waveform into a high-frequency low-voltage pulse waveform. The second power supply circuit is used to convert the high-frequency low-voltage pulse waveform in the second secondary winding into an output voltage when the first control chip outputs the PWM signal, and the output voltage is suitable for the first control chip. Controls the DC voltage that powers the chip.
5. The power conversion circuit according to claim 4, wherein the second power supply circuit comprises:

   a third rectifying and filtering circuit, the third rectifying and filtering circuit is used to convert the high-frequency low-voltage pulse waveform in the second secondary winding into a DC voltage;

   A voltage dividing filter circuit is used to filter and divide the DC voltage to generate the output voltage.
6. The power conversion circuit according to any one of claims 1-5, characterized in that, the power conversion circuit further comprises a second sampling circuit for sampling the current and voltage output by the first rectifying and filtering circuit to obtain The primary input power is obtained, and the first control chip adjusts the frequency of the PWM waveform according to the ratio of the output current to the primary input power.
7. The power conversion circuit according to claim 6, wherein the first control chip is configured as:

   Obtain the first ratio of the output current to the primary input power, when it is determined that the first ratio is less than a set threshold, adjust the frequency of the PWM waveform down to the first set value, and obtain the output again a second ratio of the current to the primary input power; when it is determined that the second ratio is greater than the first ratio, the frequency of the PWM waveform continues to be adjusted downward to the first set value; When the second ratio is smaller than the first ratio, the frequency of the PWM waveform is adjusted upward to a second set value, and the second set value is less than the first set value; after adjustment, the output current The ratio to the primary input power is maximum.
8. The power conversion circuit according to claim 7, wherein the second set value is the first set value/N ^m , N is a positive integer, and N≥2, m is a continuous callback times, m is a positive integer, and m≥1.
9. The power conversion circuit according to claim 6, wherein the first rectification filter circuit comprises:

   a first filter circuit, used for filtering out noise in the AC high-voltage power input through the power input end;

   The first rectifier circuit is used to convert the AC high voltage power after filtering out the noise into the DC high voltage power;

   a second filter circuit, configured to filter out the noise in the DC high voltage power and output the DC high voltage power after filtering the noise to the primary winding;

   The second sampling circuit includes a sampling resistor, the sampling resistor is connected in series between the positive output terminal of the first rectifier circuit and the positive output terminal of the second filter circuit, and the first control chip is connected to the sampling resistor. Both ends of the resistor are connected to collect the voltage at both ends of the sampling resistor, and obtain the primary input power according to the voltage difference between the two ends of the sampling resistor and the resistance of the sampling resistor.
10. The power conversion circuit according to claim 9, wherein the second filter circuit comprises:

    a third capacitor, the negative electrode of the third capacitor is grounded, the positive electrode of the third capacitor is connected to the positive output terminal of the first rectifier circuit, and the negative output terminal of the first rectifier circuit is grounded;

    a fourth capacitor, the negative electrode of the fourth capacitor is connected to one end of the primary winding, and the positive electrode of the fourth capacitor is connected to the other end of the primary winding;

    The sampling resistor is coupled between the positive electrode of the third capacitor and the positive electrode of the fourth capacitor.
11. An adapter, characterized by comprising the power conversion circuit according to any one of claims 1-10.

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