CN113765387A

CN113765387A - Method and apparatus for broadening voltage range of AC-DC converter

Info

Publication number: CN113765387A
Application number: CN202010487704.1A
Authority: CN
Inventors: 朱亚江; 张建志; 刘先锋
Original assignee: Shanghai Xinyi Microelectronics Co ltd; Shenzhen Transsion Holdings Co Ltd
Current assignee: Shanghai Xinyi Microelectronics Co ltd; Shenzhen Transsion Holdings Co Ltd
Priority date: 2020-06-02
Filing date: 2020-06-02
Publication date: 2021-12-07
Anticipated expiration: 2040-06-02
Also published as: CN113765387B

Abstract

The invention discloses a method and a device for improving input voltage of an alternating current-direct current converter. Comprises a rectifier, an input capacitor and a first high-voltage switch; the first high-voltage switch has two working states, and when the first high-voltage switch is in the first state, the first high-voltage switch allows the rectifier to charge the input capacitor; when the first high-voltage switch is in the second state, the first high-voltage switch prevents the rectifier from charging the input capacitor; the alternating current-direct current converter further comprises a first control circuit, wherein the first control circuit controls the working state of the first high-voltage switch according to the alternating current phase or the amplitude of the pulsating voltage; the alternating current-direct current converter based on the invention also comprises a power conversion device which comprises a transformer, a second control circuit and a second high-voltage switch and converts the periodic pulsating voltage into direct current output voltage. The invention improves the input voltage range of the AC-DC converter, reduces the volume, reduces the cost and enhances the reliability.

Description

Method and apparatus for broadening voltage range of AC-DC converter

Technical Field

The invention relates to a method and a device for improving input voltage of an alternating current-direct current converter. In particular, the present invention is directed to increasing the input voltage of an ac-dc converter, while reducing the size, cost, and reliability of the ac-dc converter, as compared to existing high voltage ac-dc converters.

Background

An ac-dc converter is a power supply device that supplies a stable dc voltage to an electronic apparatus such as a cellular phone. The input of the converter is an alternating current, and generally has two specifications of 110Vac (countries such as the united states and japan) and 220Vac (countries such as china and europe). For global travel convenience, an ac-dc converter (charger) for supplying power to portable devices such as a mobile phone has an input voltage range of 90Vac to 264Vac, and is called a full voltage range (or global scale) ac-dc converter (charger). The input voltage peak value of the global regulator charger is 1.414 x 264=375(V), so the input capacitor of the global regulator charger adopts an electrolytic capacitor with 400V withstand voltage. However, in some countries and regions (such as india), the power grid fluctuates greatly, and the single-phase ac voltage often exceeds 300Vac or even 350Vac, so that the global charger may not be safely and reliably used in india. Therefore, the input capacitor of the mobile phone charger sold to indian market needs to be increased to a withstand voltage of 500V or more, and is called a high voltage ac/dc converter or indian standard charger. 250V and 400V withstand voltage input capacitors are the most common electrolytic capacitor specifications, so 2 250V withstand voltage capacitors are generally used in series as the India charger input capacitors, as shown in FIGS. 1A and 1B. The ac-dc converter meeting the safety requirements generally adopts a design of connecting two input filter capacitors in parallel. Thus the indian charger requires two series-parallel 4 input capacitors, increasing its size by about 50% over that of a global (90Vac to 264Vac) charger. Even in this case, when the instantaneous fluctuation of the grid voltage reaches 354Vac, the voltage of the input filter capacitor of the charger still exceeds the rated withstand voltage of 500V, resulting in certain failure rate. Therefore, if the input voltage of the ac-dc converter can be increased, and at the same time, the size of the existing high-voltage ac-dc converter (charger) can be reduced, the cost of the high-voltage ac-dc converter (charger) can be reduced, and the reliability of the ac-dc converter (charger) can be enhanced, the ac-dc converter (charger) has a very positive significance for improving the use experience of the ac-dc converter (charger) in the indian market, and the purpose of the present invention is.

Fig. 1A is a simplified schematic diagram of a commercially available indian-standard ac-dc converter. Fig. 1A is a diagram of an ac-dc converter with secondary side controlling output voltage, which is commonly used in a notebook computer adapter or a mobile phone fast charger. Fig. 1A includes an ac rectifier 101 that converts ac voltage to pulsating dc voltage; the circuit comprises

input filter capacitors

102 and 103, capacitor

voltage equalizing resistors

104 and 105, a power switch 106, a power supply capacitor 107, a Pulse Width Modulation (PWM) controller 108, a current detection resistor 109, an auxiliary winding rectifier diode 110, a starting resistor 111, a transformer 120, an output capacitor 121, an output rectifier 122, an optical coupler 123, a compensation device 124, output

voltage dividing resistors

125 and 126, an optical coupler current limiting resistor 127 and a shunt regulator 128 which are connected in series. The ac voltage (90Vac to 330Vac) is rectified by the input rectifier bridge 101 and then stored in the

input capacitors

102 and 103, and the PWM controller 108 controls the power switch 106 to be turned on and off. When the power switch 106 is switched from the on state to the off state, the secondary winding charges the output capacitor 121. The secondary side voltage regulator 128 detects the output voltage through the

voltage dividing resistors

125 and 126, converts the error of the output voltage into the current of the optocoupler 123, and transmits the current from the secondary side to the primary side, and controls the duty ratio of the power switch 106 through the PWM controller 108, thereby realizing the stability of the output voltage.

Fig. 1B shows another alternative indian-standard ac-dc converter with primary side controlled output voltage (CV) and current (CC), which includes an input rectifier 101 to convert the ac voltage to pulsating dc voltage; the circuit comprises

input filter capacitors

102 and 103, series filter capacitor

voltage equalizing resistors

104 and 105, a power switch 106, a power supply capacitor 107, a primary side controller 108, output

voltage detection resistors

109 and 110, a starting resistor 111, a transformer 120, an output capacitor 121 and an output rectifier 122. The ac voltage (90Vac to 330Vac) is rectified by the input rectifier bridge 101 and then stored in the

input capacitors

102 and 103, and the primary side controller 108 controls the on and off of the power switch 106 to transfer the energy in 102 and 103 to the output capacitor 121. When the primary power switch 106 is switched from the on state to the off state, the secondary winding N_SCharging the output capacitor 121, auxiliary winding N_AThe voltage reflects the output voltage Vo, and the primary side controller 108 is connected via VS pinAnd (4) keeping the voltage of the auxiliary winding, and controlling the working state of the primary side power switch according to the error signal of Vo deviating from the target value so as to keep the output voltage stable.

In the primary side control output voltage scheme of fig. 1B, the voltage regulator 128 and the optocoupler 123 on the secondary side and auxiliary components thereof in the scheme of fig. 1A are omitted, and the primary side control output voltage scheme has the advantages of simple structure and low cost. However, the accuracy of controlling the output voltage in fig. 1B is affected by errors due to factors such as transformer coupling and sample-and-hold, and the response speed of the output voltage when the load suddenly changes is limited by the no-load operating frequency, which is a disadvantage of the scheme in fig. 1B.

The conventional approach of increasing the input voltage of the converter by means of a series input capacitance as shown in fig. 1A and 1B increases the size and cost of the converter. The high-voltage AC-DC converter based on the invention can keep the control mechanism of FIG. 1A or FIG. 1B unchanged, and the input voltage of the India standard AC-DC converter can be increased by connecting a conventional electrolytic capacitor (400V or 250V) with the high-voltage switch in series by adding a small-volume high-voltage switch and a corresponding control circuit. The added control circuit detects the output voltage (V) of the AC rectifier_IN) Or an alternating voltage (V)_AC) The timing of charging the input capacitor is selected such that the voltage of the input capacitor is less than its rated withstand voltage value (e.g., 400V or 250V), thereby increasing the input voltage of the converter and enhancing the reliability of the converter. This is the advantage of the present invention.

Disclosure of Invention

Fig. 2 shows an embodiment 200 of a high voltage ac-dc converter according to the present invention. The devices other than 203, 212, and 213, 200 are required for typical ac-dc converters. The added device of the present invention includes a high voltage switch 203 having a first port (H), a second port (L) and a control port (G) coupled to an input capacitor 202. The high voltage switch 203 has two operating states, and when the high voltage switch 203 is in the first operating state, a low resistance state is present between the first port (H) and the second port (L), allowing an ac voltage to charge the input capacitor 202. When 203 is in the second working state, the first port (H) and the second port (L) are in a high-impedance state, and the alternating voltage is forbidden to charge the input capacitor. The high voltage switch 203 has another characteristic that when the voltage at the first port (H) is lower than the voltage at the second port (L), the high voltage switch 203 presents a low resistance state from the second port (L) to the first port (H) to provide a discharge path for the input capacitor 202. The added device of the present invention further comprises an alternating current phase detection means 213 coupled to the rectifier 201. The added device of the invention further comprises a control circuit 212 having a first input port (DET) and a first output port (G). A first input (DET) of 212 is coupled to 213 and a first output (G) of 212 is coupled to the control port (G) of 203. When the voltage at the first input terminal (DET) is lower than the first reference voltage Vref1, the first output terminal (G) puts the high voltage switch 203 in a first operating state, allowing the ac voltage to charge the input capacitor 202. When the voltage at the first input terminal is higher than the first reference voltage Vref1, the first output terminal (G) puts the high voltage switch 203 in the second operating state, and prohibits the ac voltage from charging the input capacitor 202. The high voltage switch of fig. 2 is a high voltage MOS switch transistor, and a source-to-drain diode thereof can provide a discharge path for the input capacitor 202.

In the embodiment of fig. 2, the control circuit 212 is a comparator 214. The first input terminal (DET) of 212 is coupled to the negative input terminal of the comparator 214, and the positive input terminal of the comparator 214 is coupled to the first reference voltage Vref 1. A first output (G) of 212 is coupled to an output of a comparator 214. The comparator 214 may be provided with a hysteresis function to facilitate more stable switching of the operating state.

Fig. 4 is a voltage waveform of a key node in the high voltage ac/dc converter of the embodiment of fig. 2. As shown, when the instantaneous voltage of the ac VAC is lower than (1 + R204/R205) × Vref1 (e.g., 380V), the high voltage MOS switch 203 is in the first operating state (conducting state), and if the voltage of the input capacitor 202 is lower than the ac voltage, the ac voltage charges the input capacitor through the high voltage MOS switch 203, and the charging current is I_CHG(ii) a When the instantaneous voltage of the alternating current is lower than the voltage of the input capacitor, the input capacitor 202 supplies power to the primary winding of the transformer through the discharge path of 203.

Fig. 3 is another high voltage ac-dc converter embodiment 300 in accordance with the present invention. Except that 303, 304 and305, the other devices of 300 are required for typical ac-dc converters. The added device of the present invention comprises a high voltage switch 303 having a first port (H), a second port (L) and a control port (G), coupled to an input capacitor 302. The high voltage switch 303 has two operating states, when 303 is in the first operating state, a low resistance is present between the first port (H) and the second port (L), allowing an ac voltage to charge the input capacitor 302. When 303 is in the second operating state, a high impedance is present between the first port (H) and the second port (L), and the ac voltage is inhibited from charging the input capacitor 302. When the voltage at the first port (H) is lower than the voltage at the second port (L), the high voltage switch 303 presents a low resistance from the second port (L) to the first port (H), providing a discharge path for the input capacitor 302. 300 further comprises an alternating voltage phase detection means 305 coupled to the rectifier 301 for detecting the phase of the alternating voltage. 300 further includes a control circuit 304 having a first input (DET) and a first output (G) coupled to 305 and 303, respectively. When the input AC voltage is lower than the first AC voltage V for a long time_AC1(e.g., 264Vac), the control circuit 304 allows the high voltage switch 303 to be in the first operating state for the entire period of ac power (T). When the input AC voltage is higher than the first AC voltage V_AC1(e.g., 264Vac), the control circuit 304 only allows the high voltage switch 303 to operate when the instantaneous voltage of the ac is lower than the amplitude of the first ac voltage (1.414V)_AC1) In a first operating state, allowing the AC voltage to charge the input capacitor, and when the instantaneous voltage of the AC voltage is higher than the amplitude of the first AC voltage (1.414V)_AC1For example, 1.414 × 264=373(V)), the control circuit 304 prohibits the alternating current from charging the input capacitor 302.

As shown in fig. 3 and 5, in an embodiment of the present invention, the high voltage switch 303 includes a thyristor 337 and a diode 338. The anode of thyristor 337 and the cathode of diode 338 are coupled to a first port (H) of 303, the cathode of thyristor 337 and the anode of diode 338 are coupled to a second port (L) of 303, and the gate of thyristor 337 is coupled to a control port (G) of high voltage switch 303. The capacitance control circuit 304 has a first input terminal (DET) and a first output terminal (G) coupled to the phase detection circuit 305 and the high voltage switch 303, respectively. The phase detection circuit 305 includes a first voltage dividing resistor 312, a second voltage dividing resistor 313, and a third voltage dividing resistor 314. The first voltage divider resistor 312 and the second voltage divider resistor 313 may have equal resistance values (e.g., 5 mega ohms), and the third voltage divider resistor 314 may have a value of 30 kilo ohms. When the input ac voltage is zero, the voltage at the first input port of the charge control circuit 304 is approximately 0V. When the instantaneous voltage of the input ac voltage is Um × sin (2 pi ft), the first input port voltage of the charge control circuit 304 is approximately [ R314/(R314+ R312) ] × Um × sin (2 pi ft). Where Um is the amplitude of the ac voltage, f is the frequency of the ac voltage, and the resistance of R314 is much smaller than that of R312.

Fig. 5 shows a schematic diagram of the charge control circuit 304, which includes a first comparator 331 having a positive input coupled to a first reference voltage Vref1, V_AC1=[1+(R312/R314)]Vref1, the negative input of which is coupled to the first input (DET) of 304, for comparing the instantaneous voltage of the input alternating current. When the output VLINE _ LOW =1 of the first comparator 331 lasts for more than a half cycle of the alternating current, it indicates that the input alternating current is lower than the first alternating voltage V_AC1The thyristor may be in a conducting state during the entire cycle of the alternating current. When VLINE _ LOW =0, it indicates that the input alternating current is higher than the first alternating voltage V_AC1The 304 first comparator 331 makes the thyristor turn on only for a period of time after VLINE _ LOW =1 by the shaping circuit.

The schematic diagram of the charge control circuit 304 shown in fig. 5 further includes a second comparator 330 having a positive input coupled to the first input (DET) of the charge control circuit 304 and a negative input coupled to a second reference voltage Vref 2. Its input (VAC _ AZ) =1 indicates that the alternating voltage has crossed zero in the rising phase. When the input AC is lower than the first AC voltage V_AC1(e.g., 264Vac), the post Vac _ AZ =1 post control circuit 304 generates a signal G2 that triggers the conduction of the thyristor 337 via the shaping circuit, allowing 337 to be in the first operating state.

Fig. 6 is a voltage waveform of a key node in the high voltage ac/dc converter of the embodiment of fig. 3 and 4. As shown in the figure, when the alternating current V is_ACIs lower than (1 + R312/R314) Vref1 (e.g. 373V) and the duration TL is greater than (1/2) T, the second comparator 330, VLINE _ LOW =1 durationThe decision module 332, the and gate 334, and the rising edge on signal 335 generate a trigger signal G2 coupled to the control terminal G of the thyristor 337 via the or gate 336. When the input alternating current (e.g. 320Vac) is higher than V_AC1(e.g., 264Vac), the ac instantaneous voltage will always exceed 1. 414V_AC1VLINE _ LOW =0, and when the VLINE _ LOW jump becomes 1, the rising edge on signal generation module 333 generates a positive pulse G1 coupled to the control terminal G of the thyristor 337 through the or gate 336.

Drawings

Fig. 1A is a schematic diagram of a conventional switching power supply with a high input voltage secondary side controlling an output voltage.

Fig. 1B is a schematic diagram of a conventional high-input-voltage primary-side-controlled output voltage switching power supply.

Fig. 2 is a schematic diagram of a high input voltage secondary side controlled output voltage switching power supply according to the present invention.

Fig. 3 is a schematic diagram of a high input voltage primary side controlled output voltage switching power supply according to the present invention.

FIG. 4 is a waveform diagram of the main nodes of the embodiment of FIG. 2.

Fig. 5 is a schematic diagram of a first controller of the embodiment of fig. 3.

FIG. 6 is a waveform diagram of the main nodes of the embodiment of FIG. 3.

Detailed Description

Specific examples of the present invention are described in detail below. Examples of embodiments have been given in the accompanying drawings. It should be noted that the examples described herein are for illustration only and are not intended to limit the invention. Details of the implementation are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that these details need not be employed to practice the present invention. In the description of the embodiments, circuits well known in the art, such as a rising edge on signal generating module, are not specifically described in order to avoid obscuring the present invention.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment.

Fig. 2 and 3 are high input voltage ac-dc converters according to the present invention. The method comprises the following steps: the input capacitor and the control circuit thereof, the charging control switch and the phase detection circuit control the charging of the input capacitor according to the amplitude of the pulsating direct current voltage or the phase of the input alternating current voltage, so that the voltage of the input capacitor is lower than the rated withstand voltage thereof. The power conversion device is used for converting the pulsating voltage into output direct-current voltage.

The rectifier of the high input voltage ac-dc converter according to the present invention may be a full bridge rectifier as shown in fig. 2 and 3, or a half bridge rectifier. The high-voltage switch for controlling the charging of the input capacitor may be a diode formed by connecting the MOS switch and the thyristor in parallel as shown in fig. 2 and 3, or may be a bipolar switch tube, a GTO or other high-voltage power switch.

The phase detection circuit of the high input voltage AC-DC converter based on the invention can be coupled to the input or output end of the rectifier and also coupled to the primary winding (N) of the transformer_P) Or an auxiliary winding (N)_A) To obtain the direct current pulsating voltage signal or the alternating current phase signal.

According to the high-input-voltage AC-DC converter, the input capacitance control circuit can be an independent circuit, and can also be integrated with the control circuit of the power conversion device to form a single controller.

Although the embodiment is an isolated topology based on the high input voltage ac-dc converter of the present invention, the principles and apparatus of the present invention are equally applicable to topologies where the power conversion device is a non-isolated ac-dc converter.

The high input voltage ac-dc converter according to the present invention may have the capacitor charging high voltage switch as a separate packaged device, or may be integrated with the input capacitor control circuit into a single package, or integrated into the power conversion device.

While the present invention has been described in terms of the above exemplary embodiments, it is to be understood that the terminology used is intended to be in the nature of words of description and illustration, rather than of limitation. As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, but rather should be construed broadly within its spirit and scope as defined in the appended claims. Accordingly, all changes and modifications that come within the scope of the claims or the equivalents thereof are intended to be embraced therein.

Claims

1. An ac-dc converter, comprising:

an input port coupled to an alternating voltage;

an output port coupled to a load;

a rectifier coupled to the input port, converting the alternating voltage into a periodic pulsating voltage;

an input capacitor coupled to the rectifier;

a first high voltage switch coupled to the input capacitance; the first high-voltage switch has two working states, and when the first high-voltage switch is in the first state, the first high-voltage switch allows the rectifier to charge the input capacitor; when the first high-voltage switch is in the second state, the first high-voltage switch prevents the rectifier from charging the input capacitor;

the first control circuit controls the working state of the first high-voltage switch according to the alternating current phase or the amplitude of the periodic pulsating voltage;

the power conversion device comprises a transformer, a second control circuit and a second high-voltage switch, and converts the periodic pulsating voltage into direct-current output voltage.

2. An ac-dc converter according to claim 1 wherein the first high voltage switch includes a discharge path, the first high voltage switch providing a discharge path for the input capacitor when the ripple voltage is lower than the input capacitor voltage.

3. An ac-dc converter according to claim 1 and claim 2, wherein the ac-dc converter comprises a phase detection circuit coupled to the rectifier and the first control circuit; the phase detection circuit comprises a voltage divider which reduces the AC input voltage or the DC ripple voltage and provides the reduced AC input voltage or the reduced DC ripple voltage to the first control circuit.

4. An ac-dc converter according to claim 1, claim 2 and claim 3, wherein the first control circuit comprises a first comparator coupled to the phase detection circuit, the first high voltage switch and the first reference voltage; when the input voltage of the first comparator is lower than a first reference voltage, the first high-voltage switch is allowed to be in a first working state; and when the input voltage of the first comparator is higher than the first reference voltage, the first high-voltage switch is in a second working state.

5. An ac-dc converter according to claim 1, claim 2, claim 3 and claim 4, wherein the first high voltage switch is a metal-oxide-semiconductor (MOS) switch having its drain (D) coupled to the lower plate of the input capacitor, its gate (G) coupled to the first comparator output, and its source (S) coupled to the ac-dc converter input side common ground terminal; the MOS switch also includes a parasitic source-to-drain diode.

6. An AC-DC converter according to claim 1, claim 2 and claim 3, wherein the first control circuit comprises a first comparator for detecting the amplitude of the input AC voltage, the first comparator generating a first high-voltage switch ON signal when the input AC voltage crosses a first preset voltage from high to low, a low-voltage duration judging circuit for generating an enable signal when the input AC voltage is lower than the first preset voltage for more than a first preset time, and a second comparator; the second comparator is used for detecting the zero-crossing moment of the input alternating voltage, and generating a first high-voltage switch turn-on signal when the input alternating voltage is lower than a second preset voltage and the low-voltage duration judging circuit enabling signal is in an allowable state.

7. An ac-dc converter according to claim 1, claim 2, claim 3 and claim 6, wherein the first high voltage switch comprises a thyristor having its gate (G) coupled to the first control circuit output; the anode (A) of the device is coupled to the lower plate of the input capacitor; the cathode (K) of the converter is coupled to the common ground terminal of the input sides of the AC-DC converter.

8. An ac-dc converter according to claim 1, claim 2, claim 3, claim 6 and claim 7, wherein the first high voltage switch further comprises a first diode coupled to the thyristor, an anode of the diode being coupled to a cathode of the thyristor, and a cathode of the diode being coupled to an anode of the thyristor.

9. An ac-dc converter according to claim 1, claim 2 and claim 3, wherein the power conversion device can be an isolated ac-dc converter with primary side control of output voltage/current or an ac-dc converter with secondary side control of output voltage/current.

10. An ac-dc converter according to claim 1, claim 2 and claim 3, wherein the power conversion device may be a non-isolated ac-dc converter.