Power conversion device and voltage control method

Abstract

A power conversion device and a voltage control method are disclosed. The power conversion device includes a first stage circuit configured to generate a first output voltage; a second stage circuit configured to receive the first output voltage and generate an output current and a second output voltage; and a control unit configured to control the first stage circuit according to a set value of the output current, thereby adjusting the first output voltage. The present application can adapt to a wide range of load voltages by adjusting the first output voltage of the first stage circuit according to the set value of the output current of the second stage circuit.

Description

Technical Field

[0001] This invention relates to the field of power technology, and in particular to a power conversion device and a voltage control method. Background Technology

[0002] LED lighting has outstanding advantages such as energy saving and high luminous efficiency, and is therefore widely used in various lighting applications.

[0003] As high-power LED switching power supplies are designed to meet the needs of more lighting fixtures, they often require the maximum power to be met within a wide range of output voltages. For example, a 600W power conversion device needs to output 600W at full power within an output voltage range of 200V to 600V, so the constant current range of the output needs to be set between 3A and 1A.

[0004] In power supplies of this power level, a two-stage architecture is often used. The current mainstream solution is to use a PFC (power factor correction) circuit in the front stage (mainly used for constant voltage) plus a Buck circuit in the back stage (mainly used for DC-DC step-down constant current).

[0005] However, this approach has the following technical drawbacks in practical applications: the efficiency of the subsequent Buck circuit is related to the voltage difference between the input and output voltages; generally, the larger the voltage difference, the lower the efficiency. In practice, it has been found that when the output voltage of the preceding PFC circuit is constant (i.e., the input voltage of the Buck circuit is fixed), if the LED load voltage range is wide, and the output voltage of the Buck circuit is low while the output current is high, the low efficiency due to the small duty cycle of the Buck circuit often leads to a sharp increase in the losses of the switching transistor and severe heat generation. Therefore, more heat dissipation measures are needed to solve this problem.

[0006] Power supplies typically cannot accommodate a wide range of LED load voltages (e.g., a constant voltage input of 700V). When the LED load voltage is within a narrow range (e.g., 400-600V), the heat generated by the Buck circuit operating at full power in constant current mode is acceptable. However, when the LED load voltage is within a wide range (e.g., 200-600V) or 200-400V, the heat generated by the Buck circuit operating at full power in constant current mode is unacceptable. Therefore, to meet different customer needs, power supply manufacturers must produce power supplies in various specifications or make them adaptable to a wide range of load voltages, which requires heat dissipation for the switching transistors, thus increasing the cost of the power supply. Summary of the Invention

[0007] The purpose of this invention is to provide a power conversion device and a voltage control method that can solve one or more defects of the prior art.

[0008] To achieve the above objectives, the present invention provides a power conversion device comprising: a first stage circuit configured to generate a first output voltage; a second stage circuit configured to receive the first output voltage and generate an output current and a second output voltage; and a control unit configured to control the first stage circuit according to a set value of the output current, thereby adjusting the first output voltage.

[0009] In one embodiment of the present invention, when the set value of the output current is in different ranges, the first output voltage is adjusted to different voltage values.

[0010] In one embodiment of the present invention, when the set value of the output current is less than a first threshold, the first output voltage is adjusted to a first voltage value; when the set value of the output current is greater than or equal to the first threshold, the first output voltage is adjusted to a second voltage value, wherein the second voltage value is less than the first voltage value.

[0011] In one embodiment of the present invention, the power conversion device further includes: a setting unit configured to allow a user to set a setting value for the output current and to transmit the setting value of the output current to the control unit.

[0012] In one embodiment of the present invention, the setting unit is a human-computer interaction interface, and the setting unit and the control unit communicate via a serial port.

[0013] In one embodiment of the present invention, the control unit includes: a processing unit that receives a set value of the output current and outputs a first processing signal and a second processing signal; a first-level circuit control unit that receives the first processing signal and outputs a first control signal for controlling the first-level circuit; and a second-level circuit control unit that receives the second processing signal and outputs a second control signal for controlling the second-level circuit.

[0014] In one embodiment of the present invention, the first-stage circuit control unit includes: a first output voltage sampling circuit configured to sample the first output voltage and generate a first output voltage sampling signal; and a first controller configured to receive the first output voltage sampling signal and generate the first control signal to control the first-stage circuit; wherein the first processing signal is used to adjust the sampling ratio of the first output voltage sampling circuit, thereby adjusting the first output voltage.

[0015] In one embodiment of the present invention, the second-level circuit control unit is a digital control unit.

[0016] In one embodiment of the present invention, the second-stage circuit control unit is an analog integrated circuit unit, comprising: an output current sampling circuit configured to sample the output current and generate an output current sampling signal; a reference voltage generation circuit configured to receive the second processing signal and generate a reference signal; an operational amplifier configured to generate a feedback signal based on the output current sampling signal and the reference signal; and a second controller configured to receive the feedback signal and generate the second control signal to control the second-stage circuit.

[0017] In one embodiment of the present invention, the first stage circuit receives an input voltage, and the control unit is further configured to control the first stage circuit according to the input voltage, thereby adjusting the first output voltage.

[0018] In one embodiment of the present invention, when the input voltage is less than a second threshold and the set value of the output current is less than a first threshold, the control unit is configured to adjust the first output voltage to a first voltage value; when the input voltage is less than the second threshold and the set value of the output current is greater than or equal to the first threshold, the control unit is configured to adjust the first output voltage to a second voltage value; and when the input voltage is greater than or equal to the second threshold, the control unit is configured to adjust the first output voltage to the first voltage value.

[0019] To achieve the above objectives, the present invention further provides a voltage control method applied to a power conversion device, the power conversion device including a first-stage circuit, a second-stage circuit, and a control unit, wherein the voltage control method includes: configuring the first-stage circuit to generate a first output voltage; configuring the second-stage circuit to receive the first output voltage and generate an output current and a second output voltage; configuring the control unit to control the first-stage circuit according to a set value of the output current to adjust the first output voltage.

[0020] In another embodiment of the invention, when the set value of the output current is in different ranges, the first output voltage is adjusted to different voltage values.

[0021] In another embodiment of the present invention, when the set value of the output current is less than a first threshold, the control unit is configured to adjust the first output voltage to a first voltage value; when the set value of the output current is greater than or equal to the first threshold, the control unit is configured to adjust the first output voltage to a second voltage value, wherein the second voltage value is less than the first voltage value.

[0022] In another embodiment of the present invention, the voltage control method further includes: configuring a setting unit for a user to set a setting value for the output current, and transmitting the setting value of the output current to the control unit.

[0023] In another embodiment of the present invention, the setting unit is a human-computer interaction interface, and the setting unit and the control unit communicate via a serial port.

[0024] In another embodiment of the present invention, the voltage control method further includes: configuring a processing unit to receive a set value of the output current and output a first processing signal and a second processing signal; configuring a first-stage circuit control unit to receive the first processing signal and output a first control signal to control the first-stage circuit; and configuring a second-stage circuit control unit to receive the second processing signal and output a second control signal to control the second-stage circuit.

[0025] In another embodiment of the present invention, configuring the first-stage circuit control unit to receive the first processing signal and output the first control signal to control the first-stage circuit includes: configuring a first output voltage sampling circuit to sample the first output voltage and generate a first output voltage sampling signal; and configuring a first control circuit to receive the first output voltage sampling signal and generate the first control signal to control the first-stage circuit; wherein the first processing signal is used to adjust the sampling ratio of the first output voltage sampling circuit, thereby adjusting the first output voltage.

[0026] In another embodiment of the present invention, the second-level circuit control unit is a digital control unit.

[0027] In another embodiment of the present invention, the second-level circuit control unit is an analog integrated circuit unit. Configuring the second-level circuit control unit to receive the second processing signal and output the second control signal to control the second-level circuit includes: configuring an output current sampling circuit to sample the output current and generate an output current sampling signal; configuring a reference voltage generation circuit to receive the second processing signal and generate a reference signal; configuring an operational amplifier to generate a feedback signal based on the output current sampling signal and the reference signal; and configuring a second controller to receive the feedback signal and generate the second control signal to control the second-level circuit.

[0028] In another embodiment of the present invention, the voltage control method further includes: configuring the control unit to further control the first stage circuit according to the input voltage of the first stage circuit, thereby adjusting the first output voltage.

[0029] In another embodiment of the present invention, when the input voltage is less than a second threshold and the set value of the output current is less than the first threshold, the control unit is configured to adjust the first output voltage to a first voltage value; when the input voltage is less than the second threshold and the set value of the output current is greater than or equal to the first threshold, the control unit is configured to adjust the first output voltage to a second voltage value; and when the input voltage is greater than or equal to the second threshold, the control unit is configured to adjust the first output voltage to the first voltage value.

[0030] This invention can adapt to a wide range of load voltages by adjusting the first output voltage of the first stage circuit according to the set value of the output current of the second stage circuit.

[0031] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. Attached Figure Description

[0032] The above and other features and advantages of the present invention will become more apparent from a detailed description of exemplary embodiments thereof with reference to the accompanying drawings.

[0033] Figure 1 This is a circuit block diagram of the power conversion device of the present invention;

[0034] Figure 2 This is a schematic flowchart of the voltage control method for the power conversion device of the present invention;

[0035] Figure 3 This is a circuit diagram of a first preferred embodiment of the power conversion device of the present invention;

[0036] Figure 4 A schematic diagram of the output characteristics of a 600W power conversion device;

[0037] Figure 5 This is a circuit diagram of a second preferred embodiment of the power conversion device of the present invention. Detailed Implementation

[0038] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that the invention will be thorough and complete, and the concept of the exemplary embodiments will be fully conveyed to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore their detailed description will be omitted.

[0039] In describing the elements / components / etc. described and / or illustrated herein, the terms “a,” “an,” “the,” “the,” and “at least one” are used to indicate the presence of one or more elements / components / etc. The terms “comprising,” “including,” and “having” are used to indicate an open-ended inclusion and to mean that additional elements / components / etc. may exist in addition to those listed. Relative terms, such as “upper” or “lower,” may be used in the embodiments to describe the relative relationship of one component of the icon to another component. It is understood that if the device of the icon is flipped so that it is upside down, the component described as being on the “upper” side will become the component on the “lower” side. Furthermore, the terms “first,” “second,” etc., in the claims are used only as illustrative marks and are not intended to limit the number of objects to which they apply.

[0040] like Figure 1 As shown, a power conversion device 100 of the present invention includes a first-stage circuit 10, a second-stage circuit 20, and a control unit 30. The first-stage circuit 10 is configured to generate a first output voltage. The second-stage circuit 20 is configured to receive the first output voltage and generate an output current and a second output voltage. The control unit 30 is configured to control the first-stage circuit 10 according to a set value of the output current, thereby adjusting the first output voltage. The adjustment can be performed according to a set rule. For example, when the set value of the output current is in different ranges, the first output voltage can be adjusted to different voltage values. More specifically, when the set value of the output current is less than a first threshold, the first output voltage can be adjusted to, for example, the first voltage value; and when the set value of the output current is greater than or equal to the first threshold, the first output voltage can be adjusted to, for example, the second voltage value, which is less than the first voltage value.

[0041] In some embodiments of the present invention, the control unit 30 may include, for example, a processing unit 31, a first-stage circuit control unit 32, and a second-stage circuit control unit 33. The processing unit 31 receives a set value for the output current and outputs a first processing signal and a second processing signal. The first-stage circuit control unit 32 receives the first processing signal and outputs a first control signal to control the first-stage circuit 10. The second-stage circuit control unit 33 receives the second processing signal and outputs a second control signal to control the second-stage circuit 20.

[0042] Specifically, the first-stage circuit control unit 32 may include a first output voltage sampling circuit 321 and a first controller 322. The first output voltage sampling circuit 321 may be configured to sample the first output voltage and generate a first output voltage sampling signal. The first controller 322 may be configured to receive the first output voltage sampling signal and generate a first control signal to control the first-stage circuit 10. The first processing signal may be used to adjust the sampling ratio of the first output voltage sampling circuit 321.

[0043] Specifically, the second-stage circuit control unit 33 may be an analog integrated circuit unit, which may include an output current sampling circuit 331, a reference voltage generation circuit 332, an operational amplifier 333, and a second controller 334. The output current sampling circuit 331 may be configured to sample the output current and generate an output current sampling signal. The reference voltage generation circuit 332 may be configured to receive the second processing signal and generate a reference signal. The operational amplifier 333 may be configured to generate a feedback signal based on the output current sampling signal and the reference signal. The second controller 334 may be configured to receive the feedback signal and generate the second control signal to control the second-stage circuit 20. Of course, it is understood that in other embodiments, the second-stage circuit control unit 33 may also be a digital control unit, which is not intended to limit the invention.

[0044] In some embodiments of the present invention, the power conversion device 100 may further include a setting unit 40, which can be configured to allow a user to set a setting value for the output current and transmit the setting value of the output current to the control unit 30. The setting unit 40 and the control unit 30 may communicate via a serial port.

[0045] exist Figure 1 In the illustrated embodiment, preferably, the first stage circuit 10 may be a PFC circuit, the second stage circuit 20 may be a Buck circuit, the processing unit 31 may be a microprocessor (MCU), and the setting unit 40 may be a human-computer interaction interface, but the present invention is not limited thereto.

[0046] The AC input passes through the PFC circuit and generates a PFC output voltage. This PFC output voltage can be provided to the Buck circuit as its input voltage and generate an output voltage for the LED load.

[0047] The PFC output voltage is fed back to the first controller 322 via the first output voltage sampling circuit 321, and can be used to control the PFC output voltage to maintain a constant value. The first output voltage sampling circuit 321 can receive a first processing signal from the processing unit 31 (e.g., a microprocessor) to generate different sampling ratios, thereby generating different output voltage sampling signals. The first controller 322 generates different PFC output voltages based on the different output voltage sampling signals.

[0048] The output current of the Buck circuit can be sampled by the output current sampling circuit 331 to generate an output current sampling signal. The reference voltage generation circuit 332 can receive a second processing signal (e.g., a signal with different duty cycles) from the processing unit 31 (e.g., a microprocessor) to generate a reference signal. The output current sampling signal and the reference signal are processed by the operational amplifier 333 to generate a feedback signal. This feedback signal is fed back to the second controller 334, thereby generating a second control signal to keep the output current of the Buck circuit constant for use by the LED load.

[0049] The user can set the output current setting value of the Buck circuit through the human-computer interaction interface and send the output current setting value to the microprocessor, so that the microprocessor can generate the first processing signal and the second processing signal according to the set rules, so as to control the reference voltage generation circuit 332 and the first output voltage sampling circuit 321 respectively.

[0050] In some embodiments of the present invention, the first-stage circuit 10 may receive an input voltage (e.g., an AC input, but the invention is not limited thereto). The control unit 30 may be further configured to control the first-stage circuit 10 according to the input voltage of the first-stage circuit 10, thereby adjusting the first output voltage. In other words, the control unit 30 may further adjust the first output voltage according to the input voltage of the first-stage circuit 10 and a set value of the output current of the second-stage circuit. More specifically, when the input voltage of the first-stage circuit 10 is less than a second threshold and the set value of the output current of the second-stage circuit 20 is less than a first threshold, the control unit 30 may be configured to adjust the first output voltage to a first voltage value. When the input voltage of the first-stage circuit 10 is less than the second threshold and the set value of the output current of the second-stage circuit 20 is greater than or equal to the first threshold, the control unit 30 may be configured to adjust the first output voltage to a second voltage value. When the input voltage of the first-stage circuit 10 is greater than or equal to the second threshold, the control unit 30 may be configured to adjust the first output voltage to the first voltage value.

[0051] like Figure 2 As shown, the present invention correspondingly provides a voltage control method 200, which can be applied to, for example... Figure 1 The power conversion device 100 is shown. The voltage control method 200 may include: step S201, configuring a first-stage circuit to generate a first output voltage; step S202, configuring a second-stage circuit to receive the first output voltage and generate an output current and a second output voltage; step S203, configuring a control unit to control the first-stage circuit according to a set value of the output current, thereby adjusting the first output voltage.

[0052] In some embodiments of the present invention, the voltage control method 200 may further include: step S204, configuring the control unit to further control the first stage circuit according to the input voltage of the first stage circuit, thereby adjusting the first output voltage.

[0053] In some embodiments of the present invention, the voltage control method 200 may further include: configuring a setting unit for a user to set a setting value for the output current, and transmitting the setting value of the output current to the control unit.

[0054] The following will combine Figures 3-5 The power conversion device and voltage control method of the present invention will be described in more detail below.

[0055] like Figure 3 The diagram illustrates the circuit of a first preferred embodiment of the power conversion device of the present invention. Vac is the input AC voltage. BD1 is a rectifier circuit that converts the input AC voltage Vac into an input voltage Vin. Capacitor C5, inductor L1, switch S1, diode D1, and capacitor C1 together form a Boost circuit (i.e., first-stage circuit 10), which boosts the input voltage Vin to voltage VB+ (i.e., the first output voltage). The PFC controller (i.e., the first controller 322) controls the switching on and off of switch S1, thereby adjusting voltage VB+ to a stable DC voltage. Resistors R2, R3, R4, and switch S3 together form a PFC output voltage sampling circuit (i.e., the first output voltage sampling circuit 321), which generates a voltage divider Vref (i.e., the first output voltage sampling signal). When switch S3 is closed, resistors R4 and R3 are connected in parallel, forming a voltage divider ratio 1 with resistor R2, making voltage VB+ equal to voltage V1. When switch S3 is open, resistors R3 and R2 form a voltage divider ratio 2, making voltage VB+ equal to voltage V2, where voltage V2 is less than voltage V1. The desired voltage VB+ being V1 or V2 can be controlled by processing unit 31.

[0056] In this embodiment, the processing unit 31 may be a microprocessor (MCU), such as an integrated circuit unit IC1, and exchange information with the setting unit (e.g., human-machine interface) 40 through serial communication, such as receiving instruction information from the human-machine interface.

[0057] In this embodiment, switch S2, inductor L2, diode D2, and capacitor C2 form a Buck step-down circuit (i.e., second-stage circuit 20), which can be used to convert voltage VB+ into voltage V. O+ Among them, voltage V O+ It can be output to a load (e.g., an LED). The output current Io flowing through the LED passes through the sampling resistor Rs to generate an output current sampling signal (Io*Rs), which is connected to the negative terminal of operational amplifier 333. The operational amplifier 333 is, for example, an integrated circuit unit IC2.

[0058] The PWM2 port of the processing unit 31 generates a processing signal with a fixed frequency of Fs and a fixed amplitude of VDD, and an adjustable duty cycle. This processing signal is filtered by resistor R1 and capacitor C3 and converted into signal Vref2, which is then connected to the positive terminal of the operational amplifier 333 as a reference signal. The difference between the two signals (i.e., the output current sampling signal and the reference signal) is processed by the operational amplifier 333 to generate a feedback signal FB, which is sent to the Buck controller (i.e., the second controller 334). This allows the switch S2 to be turned on and off, ensuring that the current flowing through the LED is a constant value.

[0059] In this embodiment, the adjustable duty cycle processing signal of port PWM2 is generated by the microprocessor after receiving the signal from the human-machine interface, and its duty cycle can be any value from 0% to 100%.

[0060] Taking the output characteristics of a 600W power converter as an example, such as Figure 4As shown, its output voltage range is 200V to 600V, and its output current range is 1A to 3A. Within this range, it can output 600W of power. If the output current is fixed or set to Io, then its maximum output voltage is Vomax = 600W / Io, and its minimum output voltage is 0V. Since the power converter's output is controlled by a constant output current Io, but the output current Io can be set by the user through a human-machine interface, the corresponding output voltage of the power converter can be limited to between 0V and 600W / Io. For example, if the user sets the output current Io to 1A, the output voltage range is 0V to 600V. If the user sets the output current Io to 2A, the output voltage range is 0V to 300V. If the user sets the output current Io to 3A, the output voltage range is between 0V and 200V. If the user sets the output current Io to greater than 3A, the output current Io is limited to 3A, and the output voltage can only be between 0V and 200V.

[0061] Due to the need for voltage reduction, the input voltage VB+ of the Buck buck circuit must be greater than or equal to the output voltage. Since the maximum output voltage is 600V, if we assume that the set voltage VB+ is fixed at 700V, Table 1 below shows the duty cycle of the controlled switch S2 when the current is from 1A to 3A and the maximum full load power (Pomax) is 600W, operating in Continuous Conduction Mode (CCM) or Critical Conduction Mode (CRM).

[0062] As shown in Table 1, when the output voltage Vo is 200V and the output current Io is 3A, the duty cycle is only 28%. The smaller the duty cycle of the Buck circuit, the lower the efficiency and the greater the loss. Therefore, the power conversion device generates the most heat at this time, and the larger the heat sink is required.

[0063] Table 1: Comparison of Duty Cycles for Different Output Currents under 600W Conditions

[0064] Pomax Vo Io VB+ Duty 600W 600V 1A 700V 85％ 600W 400V 1.5A 700V 57％ 600W 300V 2A 700V 43％ 600W 200V 3A 700V 28％

[0065] According to the first preferred embodiment of the present invention, the ON / OFF signal of the port controlled by the microprocessor (MCU) adjusts the sampling ratio of the first output voltage sampling circuit, and controls and adjusts the output voltage VB+ of the first-stage circuit 10 as follows: As shown in Table 2, under the condition of 200V / 3A, the output voltage VB+ is reduced from 700V to 500V, and the duty cycle is increased from 28% to 40%. Under the condition of 300V / 2A, the output voltage VB+ is reduced from 700V to 500V, and the duty cycle is increased from 43% to 60%. Under the condition of 400V / 1.5A, the output voltage VB+ is reduced from 700V to 500V, and the duty cycle is increased from 57% to 80%. The increase in duty cycle helps to improve efficiency, reduce losses, and thus reduce the size of the heat sink.

[0066] Table 2: Comparison of Duty Cycles for Different Currents under 600W Conditions After VB+ Change

[0067] Pomax Vo Io VB+ Duty 600W 600V 1A 700V 85％ 600W 400V 1.5A 500V 80％ 600W 300V 2A 500V 60％ 600W 200V 3A 500V 40％

[0068] The signals of the two control ports ON / OFF and PWM2 of the microprocessor (MCU) are shown in Table 3 below.

[0069] Table 3: Status of the microprocessor's ON / OFF signal and duty cycle of the PWM2 signal under different currents at 600W.

[0070] Pomax Vo Io VB+ Duty ON / OFF PWM2 duty cycle 600W 600V 1A 700V 85％ ON 33％ 600W 400V 1.5A 500V 80％ OFF 50％ 600W 300V 2A 500V 60％ OFF 66％ 600W 200V 3A 500V 40％ OFF 100％

[0071] The output current Io does not need to be set in a point-like manner as shown in Table 3 (1A, 1.5A, 2A, 3A), but can be any value continuously within the range of 1A to 3A. For the set output current Io, the output voltage VB+ can be controlled to 700V when it is less than 1.5A, and the output voltage VB+ can be controlled to 500V when the set output current Io is greater than or equal to 1.5A. That is, when the set value of the output current Io is less than a first threshold (e.g., 1.5A), the control unit can be configured to adjust the first output voltage to a first voltage value (e.g., 700V); when the set value of the output current Io is greater than or equal to the first threshold (e.g., 1.5A), the control unit can be configured to adjust the first output voltage to a second voltage value (e.g., 500V).

[0072] like Figure 5 The diagram illustrates a circuit of a second preferred embodiment of the power conversion device of the present invention. Wherein, with Figure 3The difference between the first preferred embodiment shown is that the input voltage Vin is divided by resistors R5 and R6 to generate an input voltage sampling signal Vin_AD, which is connected to the microprocessor (MCU), and is the signal for the integrated circuit unit IC1 to detect the input voltage.

[0073] like Figure 4 As shown in Table 1 above, the output characteristics of a 600W power converter are illustrated. Furthermore, Table 1 shows the duty cycle of the controlled switch S2 when operating in either Continuous Conductive Mode (CCM) or Critical Conductive Mode (CRM) with a maximum full load power (Pomax) of 600W when the current ranges from 1A to 3A. Table 1 shows that when the output voltage Vo is 200V and the output current Io is 3A, the duty cycle is only 28%. Since the Buck circuit becomes less efficient and has higher losses with a smaller duty cycle, the power converter generates the most heat at this point, requiring a larger heatsink.

[0074] According to the second preferred embodiment of the present invention, the ON / OFF signal of the port controlled by the microprocessor (MCU) adjusts the sampling ratio of the first output voltage sampling circuit, and controls and adjusts the output voltage VB+ of the first-stage circuit 10 as follows: the input voltage Vin is divided by resistors R5 and R6 to obtain an input voltage sampling signal Vin_AD, which is then processed by the microprocessor (MCU) to obtain the value of the input voltage Vin. The input voltage Vin can be divided into two levels: Vin < 340Vrms and Vin > = 340Vrms. Since the first-stage circuit 10 is a boost circuit, its output voltage VB+ must be greater than or equal to the peak voltage of the input voltage Vin. The peak voltage of the input voltage Vin = 340Vrms is 340 * 1.4142 = 480V, which is less than the set minimum output voltage (i.e., 500V). Therefore, the first-stage circuit 10 can operate normally.

[0075] In this second preferred embodiment, as shown in Table 4 below, the present invention further sets the output voltage VB+ according to the magnitude of the input voltage Vin. Specifically, when Vin < 340Vrms, under 200V / 3A conditions, the output voltage VB+ is reduced from 700V to 500V, and the duty cycle is increased from 28% to 40%; under 300V / 2A conditions, the output voltage VB+ is reduced from 700V to 500V, and the duty cycle is increased from 43% to 60%; under 400V / 1.5A conditions, the output voltage VB+ is reduced from 700V to 500V, and the duty cycle is increased from 57% to 80%. The increase in duty cycle helps to improve efficiency and reduce losses. Furthermore, when the output voltage VB+ is reduced from 700V to 500V, the first-stage circuit 10 can also reduce the input and output voltage difference, further improving efficiency.

[0076] When Vin >= 340Vrms, since the minimum output voltage requirement of the first-stage circuit 10 is 500V, the output voltage VB+ needs to be maintained at 700V to ensure the normal operation of the first-stage circuit 10. Because the output voltage Vin is relatively high, the voltage difference between the output and input of the first-stage circuit 10 is small, and its efficiency is relatively high, so the output voltage VB+ is maintained at 700V.

[0077] Table 4: Comparison of Duty Cycles at Different Currents under 600W Conditions After VB+ Change

[0078]

[0079] The signals of the two control ports ON / OFF and PWM2 of the microprocessor (MCU) are shown in Table 5 below.

[0080] Table 5: Comparison of Duty Cycles for Different Currents under 600W Conditions After VB+ Change

[0081]

[0082] The output current Io does not need to be set in a point format as shown in Table 5 (1A, 1.5A, 2A, 3A), but can be any value continuously within the range of 1A to 3A. The output voltage VB+ can be controlled by the input voltage Vin and the set values ​​of the output current Io, as follows:

[0083] (1) When the input voltage Vin < 340Vrms and the set value of the output current Io is less than 1.5A, the output voltage VB+ is maintained at 700V;

[0084] (2) When the input voltage Vin < 340Vrms and the set value of the output current Io is greater than or equal to 1.5A, the output voltage VB+ is controlled to decrease to 500V;

[0085] (3) When the input voltage Vin>=340Vrms and the set value of the output current Io is less than 1.5A, the output voltage VB+ is maintained at 700V;

[0086] (4) When the input voltage Vin>=340Vrms and the set value of the output current Io is greater than or equal to 1.5A, the output voltage VB+ is maintained at 700V.

[0087] The two specific embodiments above are merely examples illustrating some specific implementations of the present invention, but the scope of protection of the present invention is not limited to these specific embodiments. For example, the first-stage circuit of the present invention is not limited to a Boost PFC circuit; it can also be a Flyback PFC circuit or other DC / DC circuits. Furthermore, in some other embodiments of the present invention, the present invention is not limited to adjusting the output voltage of the first-stage circuit; that is, the power conversion device of the present invention is not limited to two stages, but can also be three stages, or have no stages. The setting of the output current is also not limited to two stages, but can also be a numberless segment.

[0088] The present invention can adapt to a wide range of load voltages by adjusting the output voltage of the preceding stage (e.g., the first stage circuit) according to the set value of the output current of the subsequent stage (e.g., the second stage circuit).

[0089] Exemplary embodiments of the present invention have been specifically illustrated and described above. It should be understood that the present invention is not limited to the disclosed embodiments; rather, the present invention is intended to cover various modifications and equivalent arrangements contained within the spirit and scope of the appended claims.

Claims

1. A power conversion device, characterized in that, include: The first-stage circuit is configured to generate a first output voltage; The second-stage circuit is configured to receive the first output voltage and generate an output current and a second output voltage. The control unit is configured to control the first-stage circuit according to a set value of the output current, thereby adjusting the first output voltage. The first-stage circuit receives an input voltage, and the control unit is further configured to control the first-stage circuit based on the input voltage, thereby adjusting the first output voltage. When the input voltage is less than a second threshold and the set value of the output current is less than a first threshold, the control unit is configured to adjust the first output voltage to a first voltage value; When the input voltage is less than the second threshold and the set value of the output current is greater than or equal to the first threshold, the control unit is configured to adjust the first output voltage to the second voltage value; as well as When the input voltage is greater than or equal to the second threshold, the control unit is configured to adjust the first output voltage to the first voltage value.

2. The power conversion device according to claim 1, characterized in that, When the set value of the output current is in different ranges, the first output voltage is adjusted to different voltage values.

3. The power conversion device according to claim 2, characterized in that, in, When the set value of the output current is less than the first threshold, the first output voltage is adjusted to the first voltage value; When the set value of the output current is greater than or equal to the first threshold, the first output voltage is adjusted to a second voltage value, which is less than the first voltage value.

4. The power conversion device according to claim 1, characterized in that, Also includes: The setting unit is configured to allow the user to set the setting value of the output current and to transmit the setting value of the output current to the control unit.

5. The power conversion device according to claim 4, characterized in that, The setting unit is a human-computer interaction interface, and the setting unit and the control unit communicate via a serial port.

6. The power conversion device according to claim 1, characterized in that, The control unit includes: The processing unit receives the set value of the output current and outputs a first processing signal and a second processing signal. The first-level circuit control unit receives the first processed signal and outputs a first control signal to control the first-level circuit; and The second-level circuit control unit receives the second processing signal and outputs a second control signal to control the second-level circuit.

7. The power conversion device according to claim 6, characterized in that, The first-stage circuit control unit includes: A first output voltage sampling circuit is configured to sample the first output voltage and generate a first output voltage sampling signal; and The first controller is configured to receive the first output voltage sampling signal and generate the first control signal to control the first stage circuit. The first processing signal is used to adjust the sampling ratio of the first output voltage sampling circuit, thereby adjusting the first output voltage.

8. The power conversion device according to claim 6, characterized in that, The second-level circuit control unit is a digital control unit.

9. The power conversion device according to claim 6, characterized in that, The second-level circuit control unit is an analog integrated circuit unit, which includes: An output current sampling circuit is configured to sample the output current and generate an output current sampling signal. A reference voltage generation circuit is configured to receive the second processed signal and generate a reference signal; An operational amplifier is configured to generate a feedback signal based on the output current sampling signal and the reference signal; The second controller is configured to receive the feedback signal and generate the second control signal to control the second-stage circuit.

10. A voltage control method applied to a power conversion device, the power conversion device comprising a first-stage circuit, a second-stage circuit, and a control unit, characterized in that, The voltage control method includes: Configure the first stage circuit to generate a first output voltage; The second-stage circuit is configured to receive the first output voltage and generate an output current and a second output voltage. The control unit is configured to control the first-stage circuit according to the set value of the output current, and adjust the first output voltage. The control unit is configured to further control the first-stage circuit based on the input voltage of the first-stage circuit, thereby adjusting the first output voltage. When the input voltage is less than the second threshold and the set value of the output current is less than the first threshold, the control unit is configured to adjust the first output voltage to the first voltage value; When the input voltage is less than the second threshold and the set value of the output current is greater than or equal to the first threshold, the control unit is configured to adjust the first output voltage to the second voltage value; and When the input voltage is greater than or equal to the second threshold, the control unit is configured to adjust the first output voltage to the first voltage value.

11. The voltage control method according to claim 10, characterized in that, When the set value of the output current is in different ranges, the first output voltage is adjusted to different voltage values.

12. The voltage control method according to claim 11, characterized in that, in, When the set value of the output current is less than the first threshold, the control unit is configured to adjust the first output voltage to the first voltage value; When the set value of the output current is greater than or equal to the first threshold, the control unit is configured to adjust the first output voltage to a second voltage value, the second voltage value being less than the first voltage value.

13. The voltage control method according to claim 10, characterized in that, Also includes: The configuration setting unit allows the user to set the output current setting value and transmits the output current setting value to the control unit.

14. The voltage control method according to claim 13, characterized in that, The setting unit is a human-computer interaction interface, and the setting unit and the control unit communicate via a serial port.

15. The voltage control method according to claim 10, characterized in that, Also includes: The configuration processing unit is configured to receive the set value of the output current and output a first processing signal and a second processing signal; Configure a first-level circuit control unit to receive the first processed signal and output a first control signal to control the first-level circuit; as well as Configure a second-level circuit control unit to receive the second processing signal and output a second control signal to control the second-level circuit.

16. The voltage control method according to claim 15, characterized in that, Configuring the first-level circuit control unit to receive the first processing signal and output the first control signal to control the first-level circuit includes: Configure a first output voltage sampling circuit to sample the first output voltage and generate a first output voltage sampling signal; and The first control circuit is configured to receive the first output voltage sampling signal and generate the first control signal to control the first stage circuit. The first processing signal is used to adjust the sampling ratio of the first output voltage sampling circuit, thereby adjusting the first output voltage.

17. The voltage control method according to claim 15, characterized in that, The second-level circuit control unit is a digital control unit.

18. The voltage control method according to claim 15, characterized in that, The second-level circuit control unit is an analog integrated circuit unit. Configuring the second-level circuit control unit to receive the second processing signal and output the second control signal to control the second-level circuit includes: Configure the output current sampling circuit to sample the output current and generate an output current sampling signal; Configure a reference voltage generation circuit to receive the second processed signal and generate a reference signal; Configure the operational amplifier to generate a feedback signal based on the output current sampling signal and the reference signal; A second controller is configured to receive the feedback signal and generate the second control signal to control the second-stage circuit.

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