Wide range input and output AC-DC converter

Abstract

The present invention discloses a wide-range input-output AC-DC converter, comprising: a rectifier circuit for receiving an input AC voltage and converting it into a DC voltage, and configured to include an active switch device in at least one conductive loop; a control circuit for controlling the switch state of the active switch device according to the change of the output voltage, so as to adjust the DC voltage so that the DC voltage is proportional to the value of the output voltage; a DC-DC converter for converting the DC voltage into the output voltage. The technical solution of the present invention enables the ratio of the input electrolytic capacitor voltage to the output voltage of the subsequent DC-DC converter to be controlled within a very small range, which greatly improves the efficiency of the subsequent DC-DC converter while reducing the volume.

Description

Technical Field

[0001] The present invention relates to a power electronic technology, and more particularly to a wide range input and output AC-DC converter. Background Art

[0002] In the existing AC-DC solutions, such as Figure 1 As shown, the input AC voltage is rectified to output a voltage signal that changes periodically. A large capacitor is then used to stabilize the DC voltage after the rectifier bridge, and then the DC voltage is passed through a first-stage DCDC converter to provide the energy required by the load.

[0003] The output DC voltage Vbus of the first-stage rectifier bridge cannot be adjusted, so it changes with the input AC voltage, resulting in a wide fluctuation range. Therefore, the second-stage DCDC converter needs to adapt to a wide range of input and output voltages and cannot achieve high efficiency. Summary of the invention

[0004] In view of this, the present invention provides a wide range input and output AC-DC converter to solve the problem that the existing DCDC converter needs to adapt to a wide range of input and output voltages and cannot achieve high efficiency.

[0005] The present invention provides a wide-range input-output AC-DC converter, comprising: a rectifier circuit for receiving an input AC voltage and converting it into a DC voltage, and configured to include an active switching device in at least one conductive loop;

[0006] A control circuit, for controlling the switching state of the active switch device according to the change of the output voltage, so as to adjust the DC voltage so that the DC voltage is proportional to the value of the output voltage;

[0007] The DC-DC converter is used to convert the DC voltage into the output voltage.

[0008] Preferably, it is characterized in that the rectifier circuit is a single-phase bridge rectifier circuit, the upper tube device and the lower tube device of the same bridge arm of the single-phase bridge rectifier circuit are the active switching devices, or the two rectifier devices at two common grounds or common input ends of the single-phase bridge rectifier circuit are the active switching devices.

[0009] Preferably, it is characterized in that the active switching device has a bidirectional voltage-withstanding function.

[0010] Preferably, it is characterized in that the active switching device is a half-controlled thyristor or a fully-controlled transistor.

[0011] Preferably, it is characterized in that the control circuit obtains a reference voltage according to the output voltage.

[0012] Preferably, it is characterized in that the reference voltage is proportional to the output voltage, and the proportionality coefficient between the reference voltage and the output voltage is the ratio of the peak value when the input AC voltage is at the minimum value to the maximum value of the output voltage.

[0013] Preferably, it is characterized in that the control circuit adjusts the DC voltage by adjusting the duty cycle or the turn-on time of the active switching device according to the reference voltage, so that the ratio of the DC voltage to the output voltage approaches a predetermined ratio.

[0014] Preferably, it is characterized in that, in response to the absolute value of the input AC voltage dropping to near the reference voltage, the control circuit turns on the active switching device so that the input AC voltage can charge the input capacitor, so that the DC voltage can approach the reference voltage.

[0015] Preferably, it is characterized in that, when the active switching device is a transistor, the control circuit controls the rectifier circuit to stop working in response to the input AC voltage or input current passing through zero.

[0016] Preferably, it is characterized in that when the input AC voltage is greater than zero, when the input AC voltage drops to the sum of the reference voltage and a bias voltage, the active switching device in one of the conductive loops is turned on.

[0017] Preferably, it is characterized in that when the input AC voltage is less than zero, when the absolute value of the input AC voltage drops to the sum of the reference voltage and a bias voltage, the active switching device in another of the conductive loops is turned on.

[0018] Preferably, it is characterized in that the control circuit comprises:

[0019] A comparison circuit, used for comparing the absolute value of the input AC voltage and the sum of the reference voltage and a bias voltage, and outputting a comparison signal;

[0020] The logic circuit is used to generate a control signal of the active switch device according to the comparison signal and whether the input AC voltage is greater than zero.

[0021] The technical solution of the present invention adopts active switching devices to replace the traditional rectifier bridge, which not only makes the loss of the rectifier circuit smaller than that in the prior art, but also makes the ratio of the DC voltage to the output voltage approach a predetermined ratio by controlling the on-off of the rectifier circuit. The ratio of the input electrolytic capacitor voltage to the output voltage of the subsequent DC-DC converter is controlled within a very small range, which greatly improves the efficiency of the subsequent DC-DC converter while reducing the volume. Since the withstand voltage and volume of the input electrolytic capacitor are also reduced, the solution is very suitable for applications such as AC-DC power supplies and mobile phone chargers with high volume requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0023] Figure 1 A circuit diagram of a wide range input and output AC-DC converter of the prior art;

[0024] Figure 2 A circuit diagram of a wide range input and output AC-DC converter according to an embodiment of the present invention;

[0025] Figure 3 A circuit diagram of a wide-range input-output AC-DC converter according to another embodiment of the present invention;

[0026] Figure 4 is a circuit diagram of a control circuit according to an embodiment of the present invention;

[0027] Figure 5 1 is a working waveform diagram of a wide range input and output AC-DC converter according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The present invention is described below based on embodiments, but the present invention is not limited to these embodiments. In the detailed description of the present invention below, some specific details are described in detail. It is possible for a person skilled in the art to fully understand the present invention without the description of these details. In order to avoid confusing the essence of the present invention, known methods, processes, flows, components and circuits are not described in detail.

[0029] In addition, persons of ordinary skill in the art will appreciate that the drawings provided herein are for illustration purposes and are not necessarily drawn to scale.

[0030] At the same time, it should be understood that in the following description, "circuit" refers to a conductive loop composed of at least one element or subcircuit through electrical connection or electromagnetic connection. When an element or circuit is said to be "connected to" another element or an element / circuit is said to be "connected between" two nodes, it can be directly coupled or connected to another element or there can be an intermediate element, and the connection between the elements can be physical, logical, or a combination thereof. On the contrary, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there is no intermediate element between the two.

[0031] Unless the context clearly requires otherwise, throughout the specification and claims, the words "include", "comprising" and similar words should be interpreted in an inclusive sense rather than an exclusive or exhaustive sense; that is, in the sense of "including but not limited to".

[0032] In the description of the present invention, it should be understood that the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0033] Figure 2 2 is a circuit diagram of a wide-range input-output AC-DC converter according to an embodiment of the present invention. The wide-range input-output AC-DC converter includes a rectifier circuit 21, a control circuit 22, and a DC-DC converter 23. The rectifier circuit 21 is used to receive an input AC voltage Vac and rectify it to convert it into a DC voltage Vin, and the rectifier circuit 21 is configured to have at least one active switching device in each conductive loop. The control circuit 22 is used to adjust the DC voltage Vin according to the change of the output voltage Vo of the DC-DC converter 23, so that the ratio of the DC voltage Vin to the output voltage Vo approaches a predetermined ratio. The DC-DC converter 23, whose input port is connected to the output end of the rectifier circuit 21, is configured to adjust the DC voltage Vin output by the rectifier circuit 21 to an output voltage Vo that meets the requirements to power the load.

[0034] In an embodiment of the present invention, the rectifier circuit 21 is a single-phase bridge rectifier circuit, the upper tube device and the lower tube device of the same bridge arm of the single-phase bridge rectifier circuit are active switching devices, or the two devices with two common grounds or common input ends of the single-phase bridge rectifier circuit are active switching devices. Figure 2In the illustrated implementation example, the upper tube device and the lower tube device of the same bridge arm of the single-phase bridge rectifier circuit are active switching devices. Specifically, the upper tube of the first bridge arm is set as an active switching device S1, and the lower tube is set as an active switching device S2. Preferably, the upper tube and the lower tube of the second bridge arm are diodes D2 and D1, respectively. Of course, it can be understood that both the upper tube and the lower tube of the second bridge arm can be selected as active switching devices, or one of them can be selected as an active switching device. As long as each conductive loop of the rectifier circuit 21 has at least one active switching device.

[0035] Figure 3 This is a circuit diagram of a wide-range input-output AC-DC converter according to another embodiment of the present invention. The difference between this embodiment and the previous embodiment is that the device structure of the rectifier circuit 21 is different. Figure 3 In the illustrated implementation example, the two common ground devices of the single-phase bridge rectifier circuit are active switching devices. Of course, the devices at the two common input ends may also be active switching devices. Specifically, the lower tube of the first bridge arm is set as an active switching device S2, and the lower tube of the second bridge arm is set as an active switching device S1. Preferably, the upper tube of the first bridge arm and the upper tube of the second bridge arm are diodes D1 and D2, respectively. Of course, it is understandable that the upper tube of the first bridge arm and the upper tube of the second bridge arm may both be active switching devices, or one of them may be an active switching device. As long as there is at least one active switching device in each conductive loop of the rectifier circuit 21, it is sufficient.

[0036] Since the rectifier circuit 21 receives the input AC voltage Vac, the active switch device needs to have a bidirectional voltage-withstanding function. Preferably, the active switch device can be a half-controlled thyristor or a fully-controlled transistor.

[0037] In the embodiment of the present invention, the upper tube of the first bridge arm and the lower tube of the second bridge arm are controlled to be turned on or off synchronously, and the upper tube of the second bridge arm and the lower tube of the first bridge arm are controlled to be turned on or off synchronously in the opposite manner to the upper tube of the first bridge arm and the lower tube of the second bridge arm. Thus, the rectifier circuit 21 can rectify the input AC power Vac, and its output DC voltage Vin can be adjusted to be compatible with the output voltage Vo.

[0038] In the embodiment of the present invention, the rear stage of the rectifier circuit 21 is further connected to an input electrolytic capacitor Cin. Specifically, the input electrolytic capacitor Cin is connected between the rectifier circuit 21 and the DC-DC converter 23 to filter the output signal of the rectifier circuit 21.

[0039] Continue to see Figure 2 or Figure 3In the embodiment of the present invention, the input port of the DC-DC converter 23 is connected to the output port of the rectifier circuit 21, and is configured to convert the DC voltage Vin output by the rectifier circuit 21 into an output voltage Vo that meets the requirements to power the load, wherein the DC-DC converter 23 can be a non-isolated converter or an isolated converter, and further, a resonant converter or a multi-level converter can be selected.

[0040] The control circuit 22 is used to adjust the DC voltage Vin according to the change of the output voltage Vo of the DC-DC converter 23, so that the ratio of the DC voltage Vin to the output voltage Vo approaches the predetermined ratio. Specifically, the control circuit 22 achieves the purpose of making the ratio of the DC voltage Vin to the output voltage Vo approach the predetermined ratio by setting a reference voltage Vref representing the DC voltage Vin so that the reference voltage Vref is proportional to the output voltage Vo.

[0041] Specifically, the control circuit 22 obtains a reference voltage Vref according to the output voltage Vo. Preferably, the proportionality coefficient K between the reference voltage Vref and the output voltage Vo is the peak value Vac when the input AC voltage Vac is at the minimum value. MIN,PK The maximum value of the output voltage Vo MAX The ratio is as follows:

[0042] Vref=K·Vo(K≈Vac MIN,PK / Vo MAX )

[0043] Thus, the control circuit 22 adjusts the DC voltage Vin by adjusting the duty cycle or the conduction time of the active switch device according to the reference voltage Vref, so that the ratio of the DC voltage Vin to the output voltage Vo approaches the predetermined ratio. In this way, the ratio of the voltage of the input electrolytic capacitor Cin of the subsequent DC-DC converter to the output voltage Vo can be controlled within a very small range, which greatly improves the efficiency of the subsequent DC-DC converter 23 and reduces the volume of the DC-DC converter 23.

[0044] Preferably, in response to the absolute value |Vac| of the input AC voltage Vac dropping to near the reference voltage Vref, the control circuit 22 turns on the active switching device so that the input AC voltage Vac can charge the input electrolytic capacitor Cin, so that the DC voltage Vin can approach the voltage represented by the reference voltage Vref.

[0045] Figure 4 FIG. 1 is a circuit diagram of a control circuit according to an embodiment of the present invention. Figure 4As shown, the control circuit 22 of the embodiment of the present invention includes: an AC voltage sampling circuit 221 , a reference voltage generating circuit 222 , a comparison circuit 223 , logic circuits 224 and 225 , and drivers 226 and 227 .

[0046] Specifically, the AC voltage sampling circuit 221 is used to sample the input AC voltage Vac, obtain the absolute value |Vac| of the input AC voltage Vac, and determine whether the actual value of the input AC voltage Vac is greater than zero.

[0047] The reference voltage generating circuit 222 is used to obtain a reference voltage Vref according to the output voltage Vo or the sampling signal Vo' of the output voltage, and the proportionality coefficient between the reference voltage Vref and the output voltage Vo is the above-mentioned proportionality coefficient K. It can be understood that if the reference voltage Vref is obtained by the sampling signal Vo' of the output voltage, the proportionality coefficient between the reference voltage Vref and the sampling signal Vo' of the output voltage should be the product of the above-mentioned proportionality coefficient K and the ratio of the sampling signal Vo' of the output voltage to the output voltage Vo, in order to obtain the same ratio.

[0048] In addition, since the control circuit 22 is required to turn on the active switching device when the absolute value |Vac| of the input AC voltage Vac drops to near the reference voltage Vref, preferably, a bias voltage Voffset can be superimposed on the reference voltage Vref to obtain a first reference voltage Vref1. By comparing the absolute value |Vac| of the input AC voltage Vac and the first reference voltage Vref1, the turn-on moment of the active switching device can be obtained.

[0049] In the embodiment of the present invention, further, the reference voltage generating circuit 222 may include a proportional circuit 2221 and a superposition circuit 2222. Specifically, the proportional circuit 2221 is used to obtain the reference voltage Vref according to the output voltage Vo or the sampling signal Vo' of the output voltage, and the superposition circuit 2222 is used to superimpose an offset voltage Voffset on the reference voltage Vref to obtain a first reference voltage Vref1.

[0050] The comparison circuit 223 is used to compare whether the absolute value |Vac| of the input AC voltage Vac drops to the vicinity of the reference voltage Vref, that is, whether the absolute value |Vac| of the input AC voltage Vac drops to the first reference voltage Vref1. When dropping to, a high level comparison signal Vcmp is output.

[0051] Since the input AC voltage Vac is an AC power, its amplitude can be positive or negative, so the control of the rectifier circuit 21 can be controlled separately according to whether the input AC voltage Vac is greater than zero. When the input AC voltage Vac is greater than zero, when the input AC voltage Vac or its absolute value |Vac| drops to the first reference voltage Vref1, the active switch device in one of the conductive loops is turned on, which refers to the loop composed of Vac-diode D1-input electrolytic capacitor Cin-active switch device S1; when the input AC voltage Vac is less than zero, when the absolute value of the input AC voltage |Vac| drops to the first reference voltage Vref1, the active switch device in another conductive loop is turned on, which refers to the loop composed of Vac-diode D2-input electrolytic capacitor Cin-active switch device S2.

[0052] Based on this, the logic circuit 224 and the driver 226 can control the active switch device in one loop, for example, the active switch device S1. Correspondingly, the logic circuit 225 and the driver 227 can control the active switch device in another loop, for example, the active switch device S2. In the embodiment of the present invention, the logic circuit 224 and the logic circuit 225 are preferably implemented by an AND gate circuit.

[0053] Figure 5 FIG. 1 is a working waveform diagram of a wide range input and output AC-DC converter according to an embodiment of the present invention. Figure 5 and Figure 4When the input AC voltage Vac is greater than zero, the first input terminal of the logic circuit 224 is at a high level. When the comparison circuit 223 detects that the input AC voltage Vac or its absolute value |Vac| drops to the first reference voltage Vref1, the second input terminal of the logic circuit 224 also becomes a high level. At this time, the logic circuit 224 outputs a high-level logic signal. The driver 226 generates a drive signal V1 based on the high-level logic signal. The drive signal V1 turns on the active switch device S1, thereby turning on the loop composed of Vac-diode D1-input electrolytic capacitor Cin-active switch device S1, so that the input AC voltage Vac can charge the input electrolytic capacitor Cin, so that the DC voltage Vin can approach the reference voltage Vref. voltage; when the input AC voltage Vac is less than zero, the first input terminal of the logic circuit 225 is at a high level. When the comparison circuit 223 detects that the absolute value of the input AC voltage |Vac| drops to the first reference voltage Vref1, the second input terminal of the logic circuit 225 also becomes a high level. At this time, the logic circuit 225 outputs a high-level logic signal. The driver 227 generates a drive signal V2 based on the high-level logic signal. The drive signal V2 turns on the active switch device S2, thereby turning on the loop composed of Vac-diode D2-input electrolytic capacitor Cin-active switch device S2, so that the input AC voltage Vac can charge the input electrolytic capacitor Cin, so that the DC voltage Vin can approach the voltage represented by the reference voltage Vref. That is, in each half power frequency cycle, only the active switch device in one conductive loop is turned on.

[0054] It should be noted that when the active switch device is a transistor, the control circuit 22 can control the rectifier circuit 21 to stop working in response to the input AC voltage Vac or the input current Iac passing through zero; when the active switch device is a thyristor, since the current flowing through the thyristor will be disconnected when it is below its holding current, the thyristor does not need a special shutdown logic circuit, and it will automatically shut down near the zero crossing of the input current Iac, so that the rectifier circuit 21 also stops working. In addition, when the active switch device is a thyristor, the thyristor S1 and the thyristor S2 can be selected from unidirectional thyristors or bidirectional thyristors, both of which have bidirectional withstand voltage function. Driver 226 and driver 227 can be driven by either optocouplers or transformers.

[0055] It can be seen that the control circuit 22 obtains a reference voltage Vref by detecting the output voltage Vo, and can turn on the active switch device in response to the absolute value |Vac| of the input AC voltage Vac dropping to near the reference voltage Vref, so that the DC voltage Vin approaches the voltage represented by the reference voltage Vref, and further makes the ratio of the DC voltage Vin to the output voltage Vo approach a predetermined ratio.

[0056] The technical solution of the present invention adopts active switching devices to replace the traditional rectifier bridge, which not only makes the loss of the rectifier circuit smaller than that in the prior art, but also makes the ratio of the DC voltage to the output voltage approach a predetermined ratio by controlling the on-off of the rectifier circuit. The ratio of the input electrolytic capacitor voltage to the output voltage of the subsequent DC-DC converter is controlled within a very small range, which greatly improves the efficiency of the subsequent DC-DC converter while reducing the volume. Since the withstand voltage and volume of the input electrolytic capacitor are also reduced, the solution is very suitable for applications such as AC-DC power supplies and mobile phone chargers with high volume requirements.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A wide range input and output AC-DC converter, comprising: A rectifier circuit for receiving an input AC voltage and converting it into a DC voltage, and configured to include at least one active switching device in each conductive loop; A control circuit, for controlling the switching state of the active switch device according to the change of the output voltage, so as to adjust the DC voltage so that the DC voltage is proportional to the value of the output voltage; A DC-DC converter, used for converting the DC voltage into the output voltage; In response to the absolute value of the input AC voltage dropping to near a reference voltage, the control circuit turns on the active switching device so that the input AC voltage can charge the input capacitor, so that the DC voltage can approach the reference voltage, wherein the reference voltage is obtained according to the output voltage, and in each half power frequency cycle, only the active switching device in one conductive loop is turned on.

2. The wide-range input-output AC-DC converter according to claim 1, characterized in that: The rectifier circuit is a single-phase bridge rectifier circuit, the upper tube device and the lower tube device of the same bridge arm of the single-phase bridge rectifier circuit are the active switching devices, or the two rectifier devices at two common grounds or common input ends of the single-phase bridge rectifier circuit are the active switching devices.

3. The wide-range input-output AC-DC converter according to claim 1, characterized in that: The active switch device has a bidirectional voltage-withstanding function.

4. The wide-range input-output AC-DC converter according to claim 1, characterized in that: The active switch device is a half-controlled thyristor or a fully-controlled transistor.

5. The wide-range input-output AC-DC converter according to claim 1, characterized in that: The reference voltage is proportional to the output voltage, and a proportionality coefficient between the reference voltage and the output voltage is a ratio of a peak value when the input AC voltage is at a minimum value to a maximum value of the output voltage.

6. The wide-range input-output AC-DC converter according to claim 1, characterized in that: The control circuit adjusts the DC voltage by adjusting the duty cycle or the conduction time of the active switch device according to the reference voltage, so that the ratio of the DC voltage to the output voltage approaches a predetermined ratio.

7. The wide-range input-output AC-DC converter according to claim 1, characterized in that: When the active switch device is a transistor, the control circuit controls the rectifier circuit to stop working in response to the input AC voltage or input current passing through zero.

8. The wide-range input-output AC-DC converter according to claim 1, characterized in that: When the input AC voltage is greater than zero, when the input AC voltage drops to the sum of the reference voltage and a bias voltage, the active switching device in one of the conductive loops is turned on.

9. The wide-range input-output AC-DC converter according to claim 8, characterized in that: When the input AC voltage is less than zero, when the absolute value of the input AC voltage drops to the sum of the reference voltage and a bias voltage, the active switch device in another of the conductive loops is turned on.

10. The wide-range input-output AC-DC converter according to claim 1, characterized in that: The control circuit comprises: A comparison circuit, used for comparing the absolute value of the input AC voltage and the sum of the reference voltage and a bias voltage, and outputting a comparison signal; The logic circuit is used to generate a control signal of the active switch device according to the comparison signal and whether the input AC voltage is greater than 20 zero.

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