A high-power, wide-range adjustable DC linear regulated power supply

Abstract

This invention relates to the field of regulated power supplies, and more particularly to a high-power, wide-range adjustable DC linear regulated power supply, comprising a switching power supply input circuit, an auxiliary switching power supply circuit, a power factor compensation boost circuit, a switching power supply isolation power conversion circuit, a voltage and current controllable BUCK circuit, and a load voltage and current display circuit. Through the coordinated connection of the above-mentioned circuit modules, this invention solves the problems of narrow voltage regulation range, low power, and bulkiness of existing DC linear regulated power supplies.

Description

Technical Field

[0001] This invention relates to the field of regulated power supplies, and more particularly to a high-power, wide-range adjustable DC linear regulated power supply. Background Technology

[0002] Existing DC linear regulated power supplies suffer from narrow voltage regulation range, low power, large size, and heavy weight. A two-channel 150W laboratory DC linear regulated power supply weighs 15kg, and a two-channel 300W power supply weighs over 30kg. These existing power supplies use a series regulation method, employing transistor VCE adjustment for voltage control, resulting in high power consumption and low efficiency, especially at low voltage outputs. Overcurrent protection uses contact relay control, which suffers from insufficient power and frequent relay switching, failing to meet the requirements of inverter power supply experiments. Existing DC regulated experimental power supplies have a narrow voltage range (0-30V, with a maximum of 60V when two are used in series) and a maximum current of only 10A, which is completely insufficient for inverter circuit experiments. Summary of the Invention

[0003] Therefore, in view of the above problems, the present invention proposes a high-power, wide-range adjustable DC linear regulated power supply, which solves the problems of narrow voltage regulation range, low power, and bulkiness of existing DC linear regulated power supplies.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a high-power wide-range adjustable DC linear regulated power supply, comprising a switching power supply input circuit, an auxiliary switching power supply circuit, a power factor compensation boost circuit, a switching power supply isolation power conversion circuit, a voltage and current controllable BUCK circuit, and a load voltage and current display circuit.

[0005] The switching power supply circuit includes a short-circuit protection circuit, a first EMI circuit, a second EMI circuit, a first rectifier and filter circuit, and a second rectifier and filter circuit. The input terminal of the short-circuit protection circuit is connected to the mains power. The output terminal of the short-circuit protection circuit is electrically connected to the input terminals of the first EMI circuit and the second EMI circuit, respectively. The output terminal of the first EMI circuit is electrically connected to the input terminal of the first rectifier and filter circuit, which outputs a +300V DC voltage. The output terminal of the second EMI circuit is electrically connected to the input terminal of the second rectifier and filter circuit, which outputs a +300V DC voltage. The output terminal of the second rectifier and filter circuit is electrically connected to a power factor compensation boost circuit, which outputs a 390V DC voltage.

[0006] The auxiliary switching power supply circuit includes a switching power supply chip, an energy storage switching transformer, a line voltage detection circuit, an output power adjustment circuit, a drain clamping circuit, an auxiliary power supply rectifier and filter circuit, a precision optocoupler feedback voltage regulation control circuit, a first low-voltage rectifier and filter circuit, and a second low-voltage rectifier and filter circuit. The output terminal of the first rectifier and filter circuit is electrically connected to the energy storage switching transformer, the input terminal of the line voltage detection circuit, the input terminal of the output power adjustment circuit, and the output terminal of the drain clamping circuit, respectively. The switching power supply chip is connected to the output terminal of the line voltage detection circuit, the input terminal of the drain clamping circuit, the output terminal of the output power adjustment circuit, and the optocoupler feedback voltage regulation control circuit, respectively. The drain clamping circuit input is also electrically connected to the energy storage switch transformer input. The energy storage switch transformer output is electrically connected to the first low-voltage rectifier filter circuit input, the second low-voltage rectifier filter circuit input, and the auxiliary power supply rectifier filter circuit input. The first low-voltage rectifier filter circuit outputs a non-isolated +13.3V DC voltage, the second low-voltage rectifier filter circuit outputs an isolated +12V DC voltage, the second low-voltage rectifier filter circuit output is electrically connected to the precision optocoupler feedback voltage regulation control circuit, and the auxiliary power supply rectifier filter circuit output is electrically connected to the precision optocoupler feedback voltage regulation control circuit.

[0007] The switching power supply isolation power conversion circuit includes a dual-channel PWM signal generation circuit, an H-bridge drive circuit, a power isolation conversion circuit, a third rectifier and filter circuit, a precision optocoupler isolation voltage regulation control circuit, and an optocoupler isolation overcurrent control circuit. The output terminal of the power factor compensation boost module is electrically connected to the input terminal of the power isolation conversion circuit. The output terminal of the power isolation conversion circuit is electrically connected to the input terminal of the third rectifier and filter circuit. The output terminal of the power isolation conversion circuit is also electrically connected to the input terminal of the optocoupler isolation overcurrent control circuit and the output terminal of the H-bridge drive circuit. The output terminal of the third rectifier and filter circuit is also electrically connected to the input terminal of the precision optocoupler isolation voltage regulation control circuit. The output terminal of the optocoupler isolation overcurrent control circuit, the input terminal of the H-bridge drive circuit, and the output terminal of the precision optocoupler isolation voltage regulation control circuit are respectively electrically connected to the dual-channel PWM signal generation circuit. The first low-voltage rectifier and filter circuit is electrically connected to the dual-channel PWM signal generation circuit and the H-bridge drive circuit, respectively, to supply power to the dual-channel PWM signal generation circuit and the H-bridge drive circuit.

[0008] The voltage and current controllable BUCK circuit includes a startup circuit, a single-channel PWM generation circuit, a single-supply bootstrap level transfer isolation drive circuit, a BUCK circuit, an adjustable output voltage sampling circuit, an output current sampling circuit, a current display circuit, a voltage display circuit, and an LC filter circuit. The startup circuit, the single-supply bootstrap level transfer isolation drive circuit, and the BUCK circuit are electrically connected to the output terminal of the third rectifier filter circuit. The startup circuit is electrically connected to the single-channel PWM generation circuit. The single-channel PWM generation circuit is also electrically connected to the single-supply bootstrap level transfer isolation drive circuit, the adjustable output voltage sampling circuit, and the overcurrent protection circuit. The BUCK circuit is electrically connected to the adjustable output voltage sampling circuit and also electrically connected to the input terminal of the LC filter circuit. The output current sampling circuit is electrically connected to the output terminal of the LC filter circuit. The current display circuit is electrically connected to the output current sampling circuit, and the voltage display circuit is electrically connected to the output terminal of the LC filter circuit.

[0009] The load voltage and current display circuit includes a current amplification and comparison control circuit, an overcurrent protection circuit, and an overcurrent protection status display circuit. The current amplification and comparison control circuit is electrically connected to the current sampling circuit. The overcurrent protection circuit is electrically connected to the current amplification and comparison control circuit and to a single-channel PWM generation circuit. The overcurrent protection status display circuit, the current amplification and comparison control circuit, and the voltage display circuit are all electrically connected to the output terminal of the second low-voltage rectifier and filter circuit. The overcurrent protection status display circuit is also electrically connected to the current amplification and comparison control circuit. By adopting the aforementioned technical solutions, the beneficial effects of this invention are as follows: This high-power, wide-range adjustable DC linear regulated power supply has the advantages of a wide voltage regulation range and high power. The switching power supply input circuit provides an isolated regulated power supply to ensure the safe isolation of the power supply. A power factor compensation boost circuit is used to improve the power factor and limit the hazards of current distortion and harmonics. A single-supply bootstrap boost level transfer isolation drive circuit is used to drive the BUCK circuit, improving the dynamic range of the input voltage and reducing interference between small-signal and large-signal circuits. A simple acceleration circuit is used to improve working efficiency and reduce the complexity and cost of the drive circuit. A multi-stage LC filter circuit is used to reduce the ripple voltage of the switching power supply and improve the performance of the linear power supply. An ultra-low value current sampling resistor is used to sample the load current, reducing the power loss of the sampling resistor. A current amplification and comparison control circuit is used to amplify the sampled current and generate an overcurrent protection control voltage after comparison, realizing contactless overcurrent protection and enhancing the reliability of the circuit. Attached Figure Description

[0010] Figure 1 This is a circuit structure block diagram of an embodiment of the present invention;

[0011] Figure 2This is a circuit schematic diagram of the switching power supply input circuit according to an embodiment of the present invention;

[0012] Figure 3 This is a circuit diagram of the auxiliary switching power supply circuit according to an embodiment of the present invention;

[0013] Figure 4 This is a circuit diagram of the power factor compensation boost circuit according to an embodiment of the present invention;

[0014] Figure 5 This is a circuit schematic diagram of the switching power supply isolation power conversion circuit according to an embodiment of the present invention;

[0015] Figure 6 This is a circuit diagram of the voltage and current controllable BUCK circuit and the load voltage and current display circuit according to an embodiment of the present invention. Detailed Implementation

[0016] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0017] refer to Figures 1-6 This embodiment provides a high-power, wide-range adjustable DC linear regulated power supply, including a switching power supply input circuit 1, an auxiliary switching power supply circuit 2, a power factor compensation boost circuit 3, a switching power supply isolation power conversion circuit 4, a voltage and current controllable BUCK circuit 5, and a load voltage and current display circuit 6.

[0018] like Figure 2 The switching power supply input circuit 1 includes a short-circuit protection circuit 11, a first EMI circuit 12, a second EMI circuit 13, a first rectifier and filter circuit 15, and a second rectifier and filter circuit 14. To reduce mutual interference, it consists of two sets of EMI circuits and two independent rectifier and filter circuits for isolated power supply. P1 is the mains input terminal block, F1 is a fuse for short-circuit protection, Rt1 is a negative temperature coefficient thermistor to reduce the impact on the power grid during startup, and Rv1 is a varistor to prevent lightning strikes. L2, C4, and C1 form the first EMI circuit 12, which prevents grid interference signals from entering the high-power isolated switching power supply and the interference generated by the high-power isolated switching power supply from entering the grid. The first rectifier filter circuit 14 uses a rectifier silicon stack D2, and C2 is a filter capacitor. In order to improve the power factor, a power factor compensation circuit is used, so the capacitance of C2 should not be too large, so it provides a large current DC voltage with large ripple. L3, C17, and C19 form the second EMI circuit 13, which prevents grid interference signals from entering the auxiliary switching power supply and the interference generated by the auxiliary switching power supply from entering the grid, as well as the crosstalk between the high-power isolated switching power supply and the auxiliary switching power supply. D14 to D17 form the second rectifier filter circuit 15, and C36 is a filter capacitor, which provides a small current DC voltage with smaller ripple.

[0019] The connection method of the above-mentioned switching power supply module 1 is as follows: the input terminal of the short-circuit protection circuit 11 is connected to the mains power, the output terminal of the short-circuit protection circuit 11 is electrically connected to the input terminal of the first EMI circuit 12 and the input terminal of the second EMI circuit 13, the output terminal of the first EMI circuit 12 is electrically connected to the input terminal of the first rectifier and filter circuit 15, and the output terminal of the first rectifier and filter circuit 15 outputs a +300V DC voltage, the output terminal of the second EMI circuit 13 is electrically connected to the input terminal of the second rectifier and filter circuit 14, and the output terminal of the second rectifier and filter circuit 14 outputs a +300V DC voltage, the output terminal of the second rectifier and filter circuit 14 is electrically connected to the power factor compensation boost circuit 3, and the output terminal of the power factor compensation boost circuit 3 outputs a 390V DC voltage.

[0020] like Figure 3The auxiliary switching power supply circuit 2 includes a switching power supply chip 20, an output power adjustment circuit 21, a line voltage detection circuit 22, a drain clamping circuit 23, an auxiliary power supply rectification and filtering circuit 24, an energy storage switching transformer 25, a precision optocoupler feedback voltage regulation control circuit 26, a first low-voltage rectification and filtering circuit 27, and a second low-voltage rectification and filtering circuit 28. The switching power supply chip 20 (IC19 in the figure) uses the TOP246Y switching power supply control chip. Resistor R77 forms the line voltage detection circuit 22, providing overvoltage and undervoltage protection. Resistor R76 and potentiometer RP10 form the output power adjustment circuit 21. Resistor R52, high-voltage ceramic capacitor C45, fast recovery diode D23, and Zener diode DS6 form the drain clamping circuit 23 to prevent damage to the switching power supply control chip due to voltage spikes caused by leakage inductance. Schottky diode D21, common-mode inductor L5, common-mode inductor L15, resistor R48, ceramic capacitors C39, C46, ​​C47, and C171, and... Electrolytic capacitors C42, C43, and C170 form the first low-voltage rectifier and filter circuit 27, which reduces output voltage ripple and minimizes interference between the non-isolated +13.3V power supply and the isolated +12V power supply, providing the non-isolated +13.3V power supply for the power factor compensation boost circuit 3, the dual-channel PWM signal generation circuit, and the H-bridge drive circuit. Schottky diode D24, common-mode inductor L9, resistor R54, ceramic capacitors C50, C58, and C59, and electrolytic capacitors C56 and C57 form the second low-voltage rectifier and filter circuit 28, which provides power for the current amplification and comparison control circuit 60, the overcurrent protection status display circuit 62, and the voltage display circuit. Schottky diode D26 and electrolytic capacitor C60 form the auxiliary power supply rectification and filtering circuit 24, providing control voltage. Optocoupler IC13, precision three-terminal regulator IC15, resistors R62, R69, R70, R79, R80, R82, R92, ceramic capacitors C66 and C82, high-voltage ceramic capacitor C83, and electrolytic capacitors C69 and C79 constitute the precision optocoupler feedback voltage regulation control circuit 26, stabilizing the isolated output voltage at +12V. Electrolytic capacitor C69 is a soft-start capacitor, resistors R62 and R80 are isolation resistors, and electrolytic capacitor C79, ceramic capacitor C82, and resistor R92 form a dual-time-constant low-pass filter to reduce interference to the control terminal and improve circuit stability. High-voltage ceramic capacitor C83 is a safety capacitor to reduce potential drift.

[0021] The connection method of the above-mentioned auxiliary switching power supply circuit 2 is as follows: the output terminal of the first rectifier filter circuit 15 is electrically connected to the energy storage switching transformer 25, the input terminal of the line voltage detection circuit 22, the output terminal of the drain clamping circuit 23, and the input terminal of the output power adjustment circuit 21, respectively. The switching power supply chip 20 is electrically connected to the output terminal of the line voltage detection circuit 22, the input terminal of the drain clamping circuit 23, the output terminal of the output power adjustment circuit 21, and the precision optocoupler feedback voltage regulation control circuit 26, respectively. The input terminal of the drain clamping circuit 23 is also electrically connected to the input terminal of the energy storage switching transformer 25. The output terminal of the energy storage switching transformer 25 is connected to the input terminal of the first low-voltage rectifier filter circuit 27, the input terminal of the second low-voltage rectifier filter circuit 28, and the auxiliary power supply circuit 26, respectively. The input terminal of the source rectifier filter circuit 24 is electrically connected. The output terminal of the first low-voltage rectifier filter circuit 27 outputs a non-isolated +13.3V DC voltage to power the dual-channel PWM signal generation circuit 41 and H-bridge drive circuit 42 of the power factor compensation boost circuit 3 and the switching power supply isolation power conversion circuit 4. The output terminal of the second low-voltage rectifier filter circuit 28 outputs an isolated +12V DC voltage to power the overcurrent protection status display circuit 62, the current amplification comparison control circuit 60, and the voltage display circuit 57. The output terminal of the second low-voltage rectifier filter circuit 28 is electrically connected to the precision optocoupler feedback voltage regulation control circuit 26. The output terminal of the auxiliary power supply rectifier filter circuit 24 is electrically connected to the precision optocoupler feedback voltage regulation control circuit 26.

[0022] like Figure 4The power factor compensation boost circuit 3 is a BOOST topology. Inductor L1 is a series energy storage inductor, MOSFET Q1 is a parallel switching transistor, rectifier diode D1 is a Schottky diode, serving rectification and isolation purposes, and electrolytic capacitor C1 is a filter capacitor. Resistors R2 and R26, potentiometer RP1, and ceramic capacitor C35 form a voltage feedback / shutdown circuit, feeding the output voltage back to pin 1 of the power factor compensation control chip IC5 (NCP1653), providing output voltage regulation and overvoltage protection. The normal voltage range of this pin is below 2.5V. When the output voltage rises or becomes overvoltage, there is no drive signal output at pin 7, providing overvoltage protection. When the output voltage is low, or the feedback resistor is open, the voltage at pin 1 decreases, and the chip shuts down, entering a low-power operating mode. Adjusting the potentiometer RP1 changes the output voltage. Ceramic capacitor C33 is a control voltage / soft-start capacitor. The control voltage controls the input impedance to achieve power factor correction. When the power is on, the voltage at this pin gradually increases, allowing the duty cycle of the drive output to gradually increase, achieving a soft-start effect. Resistors R1 and R24, and ceramic capacitors C32 and C34 form an input voltage detection circuit. When the detected input voltage is below 2.4V, the power supply is in undervoltage protection mode, and there is no output. Constantan wire resistor R42 is a current sampling resistor, and resistor R40 is an overcurrent protection detection isolation resistor. When the current flowing through resistor R40 reaches 200 microamps, there is no output. Resistor R41 and ceramic capacitor C30 are external resistors and capacitors connected to the multiplier voltage Vm, operating in average current type PFC mode, providing a voltage VM for PFC duty cycle modulation. The input impedance of the PFC input circuit is proportional to the external resistor R41 connected to this terminal. Resistor R23 is the isolation resistor for the DRV output drive signal. Ceramic capacitor C13 is the accelerating capacitor, which makes the leading and trailing edges of the drive pulse steep, accelerating the turn-on and turn-off of the parallel switch Q1, reducing losses and improving efficiency. Resistor R7 is the discharge resistor for the junction capacitance of the parallel switch Q1. Zener diode DS1 is the limiting Zener diode, which reduces the amplitude of interference pulses, protecting the parallel switch Q1 and improving efficiency. Resistor R3, electrolytic capacitor C5, and ceramic capacitor C7 form the decoupling circuit for pin 8 (VCC) of the power factor compensation control chip IC5, providing the chip's operating voltage (8.75-18V).

[0023] like Figure 5 The switching power supply isolation power conversion circuit 4 includes a dual-channel PWM signal generation circuit 41, an H-bridge drive circuit 42, an isolation conversion circuit 43, an optocoupler isolation overcurrent control circuit 44, a precision optocoupler isolation voltage regulation control circuit 45, and a third rectifier and filter circuit 46.

[0024] The dual-channel PWM signal generation circuit 41 consists of a pulse width modulation chip TL494 and its peripheral components, generating two complementary PWM signals. The pulse width of the PWM signal is controlled by the voltage at pin 1 of the pulse width modulation chip IC2. Whether there is an output is controlled by the overcurrent control at pin 16 and the soft-start control at pin 4 of the pulse width modulation chip IC2. Electrolytic capacitor C6 and resistor R37 form the soft-start circuit. When pin 4 of the pulse width modulation chip IC2 is high, there is no output. Resistor R43 limits the current, optocoupler IC1 provides isolation control, and Zener diode DS8 raises the control threshold voltage to reduce the impact on other circuits. When the overcurrent protection control signal SD is high, the output of the drive circuit and the PWM signal generation circuit are shut off, providing overcurrent protection for the contactless switch. Ceramic capacitor C14, potentiometer RP4, and resistor R36 form the timing circuit of the RC oscillation circuit. Ceramic capacitor C14 is the timing capacitor, and potentiometer RP4 and resistor R36 are the timing resistors. Changing potentiometer RP4 changes the sawtooth wave frequency. Transistors Q4 and Q6, diodes D8 and D10, and resistors R33 and R34 constitute an acceleration circuit. D8 and D10 are isolation diodes. During the low-level output of pins 9 and 10 of the pulse width modulation chip IC2, transistors Q6 and Q4 are rapidly turned on and discharged, while diodes D8 and D10 are turned off. During the high-level output of pins 9 and 10 of IC2, transistors Q4 and Q6 are rapidly turned off, while diodes D10 and D8 are rapidly turned on. Resistor R18, electrolytic capacitor C15, and ceramic capacitor C16 form the power supply decoupling circuit for the pulse width modulation chip IC2.

[0025] The H-bridge driver circuit 42 uses two half-bridge driver chips IR2110 (IC3, IC7) to drive the two-sided field-effect transistors Q2, Q3, Q5, and Q7 of the full bridge alternately according to the drive signal PWM wave, outputting a power-amplified PWM wave. In the diagram, diode D4 and electrolytic capacitor C11, and diode D13 and electrolytic capacitor C31 are the boost isolation diode and bootstrap capacitor, respectively. Resistors R12, electrolytic capacitor C10, ceramic capacitor C18, and resistors R31, electrolytic capacitor C25, and ceramic capacitor C37 form a power supply decoupling circuit to reduce power supply interference between components. Resistors R11, R30, R38, and R48 are isolation resistors; if too large, the pulse leading-out time will be too long, increasing losses; if too small, the current switching transistor will oscillate excessively. Ceramic capacitors C9, C20, C27, and C38 are accelerating capacitors, and diodes D34, D35, D36, and D37 are Schottky diodes, accelerating the discharge of the gate-source junction capacitance of the current switching transistor.

[0026] The isolation converter circuit 43 consists of an isolation transformer T1, current switching transistors Q2, Q3, Q5, and Q7, etc., to realize high-power DC-DC conversion. Resistors R15, R29, R39, and R45 are discharge resistors, and Zener diodes DS2, DS3, DS4, and DS5 are limiting Zener diodes to reduce the amplitude of interference pulses, protect current switching transistors Q2, Q3, Q5, and Q7, and improve efficiency. Resistor R47 is a current sampling resistor. The above components are included to improve efficiency. Resistor R27 is an isolation resistor, and diode D7 is an isolation diode.

[0027] The optocoupler-isolated overcurrent control circuit 44 consists of resistors R6, R10, R13, R14, R27, optocoupler IC1, ceramic capacitor C3, switching diodes D3 and D7, and Zener diode DS7. Resistors R10 and R14 form a voltage divider circuit to provide the overcurrent protection reference voltage. Switching diodes D3 and D7 are connected to resistor R6 via a logical OR relationship, and resistor R6 acts as a pull-down resistor. Ceramic capacitor C3 is a filter capacitor; any overcurrent in any part of the circuit will trigger the protection circuit. Optocoupler IC1 provides isolation control, and Zener diode DS7 raises the control threshold voltage, reducing the impact on other circuits.

[0028] The precision optocoupler isolation voltage regulator control circuit 45 is composed of resistors R5, R9, R16, R17, R19, R20, R21, R22, R25, R28, R32, R35, optocoupler IC4, precision three-terminal voltage regulator IC6, ceramic capacitors C8, C12, C24, electrolytic capacitor C26, and other components. Resistors R9 and R19 form a voltage divider circuit to provide a reference voltage. Ceramic capacitor C12 is an integrating negative feedback capacitor, forming a PI amplifier with the internal amplifier 1 of the pulse width modulation chip IC2 to achieve voltage regulation control. Resistors R16 and R22 form an output voltage divider circuit; R16 acts as a step-down and current-limiting resistor, R22 as a voltage limiter, R21 as an isolation resistor, and R28 as a current shunt resistor, improving the linearity of optocoupler IC4. Resistors R17, R25, and R35 form an output voltage sampling circuit, providing a comparison signal to the precision voltage regulator IC6. Adjusting the output voltage of IC6 changes the drive current of the LED in the optocoupler, thereby changing the conduction level of the phototransistor in the optocoupler, providing a comparison signal to pin 1 of the pulse width modulation chip IC2 to achieve voltage regulation control. Ceramic capacitor C8 is a filter capacitor to reduce interference and improve voltage regulation stability. Resistor R32 is the load resistor for optocoupler IC4. High-voltage ceramic capacitor C28 is a safety capacitor to reduce potential drift.

[0029] The third rectifier and filter circuit 46 consists of three-terminal diodes D5, D6, D9, D11, common-mode inductor L4, ceramic capacitors C14 and C22, and electrolytic capacitors C21 and C23. It rectifies the alternating PWM voltage into a DC PWM voltage. After filtering out high-order harmonics by the filter composed of common-mode inductor L4, ceramic capacitors C14 and C22, and electrolytic capacitors C21 and C23, it becomes a smooth DC output, which is used by the voltage and current controllable BUCK circuit 5.

[0030] The circuit connection method of the above-mentioned switching power supply isolation power conversion circuit 4 is as follows: the output terminal of the power factor compensation boost module 3 is electrically connected to the input terminal of the power isolation conversion circuit 43; the output terminal of the power isolation conversion circuit 43 is electrically connected to the input terminal of the optocoupler isolation overcurrent control circuit 44, the input terminal of the third rectifier filter circuit 46, and the input terminal of the H-bridge drive circuit 42, respectively; the output terminal of the third rectifier filter circuit 46 is electrically connected to the input terminal of the precision optocoupler isolation voltage regulation control circuit 45; the output terminal of the optocoupler isolation overcurrent control circuit 44, the input terminal of the H-bridge drive circuit 42, and the output terminal of the precision optocoupler isolation voltage regulation control circuit 45 are electrically connected to the dual-channel PWM signal generation circuit 41, respectively; and the first low-voltage rectifier filter circuit 27 is electrically connected to the dual-channel PWM signal generation circuit 41 and the H-bridge drive circuit 42, providing power to the dual-channel PWM signal generation circuit H-bridge drive circuit 42.

[0031] The above Figure 6 The circuit diagram shows the voltage and current controllable BUCK circuit 5 and the load voltage and current display circuit 6. The voltage and current controllable BUCK circuit 5 includes a startup circuit 50, a single-channel PWM generation circuit 51, a single-supply bootstrap voltage transfer isolation drive circuit 52, a BUCK circuit 53, an LC filter circuit 54, an output voltage adjustable sampling circuit 55, an output current sampling circuit 56, a voltage display circuit 57, and a current display circuit 58.

[0032] The startup circuit 1 consists of a resistor R1, an electrolytic capacitor C1, a ceramic capacitor C2, and an undervoltage lockout circuit within the pulse width modulation chip IC2 (UC3842). Resistor R1 is the startup resistor, serving as a voltage reduction and current limiting resistor. Its design can be tailored to the input voltage level. The startup threshold voltage is 16V, the minimum operating voltage is 10V, the startup current is less than 1mA, and the oscillator discharge current is less than 10mA. Since the output of this circuit is used to drive the LED within the optocoupler, the power consumption is very low, eliminating the need for additional power supply circuits and simplifying the startup circuit. Electrolytic capacitor C1 and ceramic capacitor C2 are decoupling capacitors. When the power supply charges electrolytic capacitor C1 and ceramic capacitor C2 through the startup resistor R1, and the charging voltage exceeds 16V, the internal 5V regulated power supply starts operating. When the power supply starts charging electrolytic capacitor C1 and ceramic capacitor C2 through the startup resistor R1, and the charging voltage is less than 10V, undervoltage lockout occurs, and operation stops.

[0033] The single-channel PWM generation circuit 51 consists of a sawtooth wave generation circuit, a feedback voltage PI circuit, and an overcurrent protection circuit. When the VCC voltage at pin 7 of the PWM chip IC2 exceeds 16V, the internal regulator starts working, outputting a 5V reference voltage from pin 8. This voltage charges the ceramic capacitor C14 through resistor R4, forming a sawtooth wave voltage. Resistor R4 and ceramic capacitor C14 form the timing circuit for the sawtooth wave generation, determining the oscillation frequency. Resistor R10, non-polarized capacitor C6, and the internal error amplifier of IC2 form a proportional-integral amplifier circuit, which proportionally amplifies the adjustable sampling signal of the output voltage and compares it with the sawtooth voltage to generate the PWM signal, achieving closed-loop voltage regulation control. Resistor R15 is a pull-down resistor, and non-polarized capacitor C15 is a high-frequency filter capacitor. The overcurrent control signal SD, which is sampled, amplified, and compared with the output load current, provides a voltage higher than 1V to pin 3 of the PWM chip IC2 through the overcurrent protection control circuit, shutting off the PWM output and providing overcurrent protection.

[0034] The single-supply bootstrap level transfer isolation drive circuit 52 is composed of components such as optocoupler IC3, PNP transistors Q2 and Q3. Optocoupler IC3 realizes level transfer isolation control, and resistor R5 and ceramic capacitor C9 are acceleration circuits that increase the steepness of the PWM pulse leading and trailing edges, shorten the rise and fall times, reduce losses, and improve power efficiency. PNP transistor Q2 is the driver transistor, PNP transistor Q3 is the bleeder and accelerator transistor, diode D3 is the isolation diode, resistor R3 is the voltage reduction and current limiting protection resistor, resistor R2 is the reverse bias resistor to ensure that the driver transistor Q2 is cut off when there is no PWM signal, R12 is the bias resistor for PNP transistor Q3, and Zener diode DS1 is the clamping protection diode to protect the gate and source of the series switch Q1 in the BUCK circuit from excessive voltage breakdown during the high level of the PWM signal, especially at the beginning of startup when there is no output voltage and the gate and source of switch Q1 bear the entire input voltage, making it extremely easy to break down the gate and source of switch Q1. Therefore, the parameter settings of resistor R3 and Zener diode DS1 are crucial to the safe and reliable operation of this circuit. When the PWM is high level, the series switch Q1 is turned on, and the source voltage is approximately equal to the input voltage VIN. If the gate voltage is not raised, the series switch Q1 will be turned off by itself and cannot conduct continuously. To keep Q1 continuously on, the gate-source voltage must be increased. This can be achieved using an independent power supply or a bootstrap voltage boost circuit. Using an independent power supply increases circuit complexity and cost, while using a bootstrap voltage boost circuit is the simplest and most effective method, requiring fewer components and lowering costs. Diode D1 and electrolytic capacitor C3 form a bootstrap voltage boosting circuit. During the low-level PWM period, the internal LED and phototransistor of the optocoupler are cut off, as are PNP transistor Q2 and isolation diode D3. The input power supply VIN charges electrolytic capacitor C5 through isolation diode D1. The charging voltage is close to the power supply voltage, and PNP transistor Q3 saturates and conducts, quickly discharging the gate-source charge of series switch Q1, ensuring that series switch Q1 is quickly cut off, making the falling edge of the PWM pulse steep and improving power efficiency. During the high-level PWM period, the internal LED and phototransistor of the optocoupler are turned on, and PNP transistor Q2 and isolation diode D3 also turn on. The gate-source of series switch Q1 receives a driving voltage and also turns on, increasing the output voltage. Since the voltage across electrolytic capacitor C3 cannot change abruptly, the emitter potential of PNP transistor Q2 also increases. The voltage of electrolytic capacitor C3 supplies power to maintain the conduction of series switch Q1. At this time, isolation diode D1 is reverse biased and cut off. The selection of circuit parameters for this part should be based on the highest input voltage, choosing optocouplers and PNP transistors with higher voltage resistance.

[0035] The BUCK circuit 53 consists of a series switch Q1, a freewheeling diode D5, a filter inductor L1, and a filter electrolytic capacitor C4. Their parameters can be selected according to power design requirements. The rated current of the series switch Q1 is generally selected to be 1.5 to 2 times the actual current, and its drain-source voltage should generally be greater than or equal to 2 to 3 times the input voltage. The forward rated current of the freewheeling diode D5 must be equal to the maximum drain current of the series switch, i.e., greater than the load current. The reverse withstand voltage of the freewheeling diode D5 should generally be greater than or equal to 2 to 3 times the input voltage. The minimum filter inductance L1 can be calculated using the following formula:

[0036] In the formula U O To output DC voltage, U I Where is the input voltage, f is the operating frequency of the switching power supply, and I... Omin This is the minimum load current.

[0037] The filter capacitor C4 can be adjusted according to the required AC component of the output voltage ΔU. O The results, along with other given design data, are calculated using the following formula:

[0038] Therefore, choosing a higher switching frequency can reduce the filter inductance and filter capacitance, reduce size and weight, and increase the power density of the BUCK circuit.

[0039] The LC filter circuit 54 further reduces output voltage ripple. After passing through two LC filters, inductors L2 and L3 are small-capacity inductors, electrolytic capacitors C5 and C6 are filter capacitors, and non-polar capacitors C7 and C18 are high-frequency filter capacitors. The filtering effect also depends on the location of the feedback voltage connection to the output. The optimal solution is to connect it to the output terminal of the energy storage inductor, because the ripple of the energy storage inductor is the largest and unavoidable; subsequent filtering can greatly reduce the ripple voltage. If the feedback voltage is connected to the regulated output terminal, the subsequent inductor is also treated as an energy storage inductor, and ripple voltage is unavoidable.

[0040] The adjustable output voltage sampling circuit 55 consists of resistor R13 and potentiometer RP1. It samples the output voltage and feeds it back to pin 2 of the pulse width modulation chip IC2 to achieve closed-loop voltage regulation control. Adjusting the potentiometer RP1 changes the magnitude of the output DC voltage. The output voltage can be calculated using the following formula:

[0041]

[0042] The output current sampling circuit 56 consists of a current sampling resistor R16, and a 5mΩ constantan wire is used to reduce losses.

[0043] The circuit connection of the voltage and current controllable BUCK circuit 5 is as follows: the startup circuit 50, the single-supply bootstrap level transfer isolation drive circuit 52, and the BUCK circuit 53 are electrically connected to the output terminal of the third rectifier filter circuit 46, respectively. The startup circuit 50 is electrically connected to the single-channel PWM generation circuit 51. The single-channel PWM generation circuit 51 is also electrically connected to the single-supply bootstrap level transfer isolation drive circuit 52, the output voltage adjustable sampling circuit 55, and the overcurrent protection circuit 61, respectively. The BUCK circuit 53 is connected to the input terminal of the LC filter circuit 54. The output voltage adjustable sampling circuit 55, the voltage display circuit 57, and the output current sampling circuit 56 are electrically connected to the output terminal of the LC filter circuit 54, respectively. The current display circuit 58 is electrically connected to the output current sampling circuit 56.

[0044] The aforementioned switching power supply input circuit 1, auxiliary switching power supply circuit 2, power factor compensation boost circuit 3, switching power supply isolation power conversion circuit 4, and voltage and current controllable BUCK circuit 5 are all existing known technologies.

[0045] The load voltage and current display circuit 6 includes a current amplification and comparison control circuit 60, an overcurrent protection circuit 61, and an overcurrent protection status display circuit 62.

[0046] The current amplification and comparator control circuit 60 consists of an integrated operational amplifier chip IC4 (LM358) and its peripheral components. Resistor R9 is an isolation resistor, and electrolytic capacitor C16 and ceramic capacitor C17 are filter capacitors. The output current is sampled and applied to the non-inverting input of integrated operational amplifier 1. Potentiometer RP2 and resistor R19 form a negative feedback network. Adjusting potentiometer RP2 can change the voltage amplification factor. Due to the large current dynamic range, the amplification factor is changed for amplification. A large amplification factor is used for small currents, and a small amplification factor is used for large currents. The comparator uses a fixed voltage method. Resistors R10 and R21 divide the voltage to apply a fixed bias voltage to the inverting input of integrated operational amplifier 2. When the set current is not overcurrent, the output of integrated operational amplifier 2 outputs an overcurrent control signal SD at a low level, and all circuits are in normal working state. When the set current is overcurrent, the output of integrated operational amplifier 2 outputs an overcurrent control signal SD at a high level, and all circuits are in the off state, realizing contactless overcurrent protection. Diode D4 is an isolation diode, resistor R8 is an isolation resistor, and resistor R20 is a pull-down resistor.

[0047] The overcurrent protection circuit 61 consists of a control switch NPN transistor Q4, isolation resistors R18 and R22, and a Zener diode DS2. When the circuit is operating normally without overcurrent, when the overcurrent control signal SD is low, both the control switch NPN transistor Q4 and the Zener diode DS2 are cut off, which does not affect the circuit operation. When the overcurrent control signal SD is high, both the control switch NPN transistor Q4 and the Zener diode DS2 are turned on, shutting down the single-channel PWM signal output, cutting off the power supply, and providing overcurrent protection.

[0048] The overcurrent protection status display circuit 62 consists of NPN transistors Q11 and Q12, resistors R45, R46, R47, and R48, a red LED diode DS5, and a green LED diode DS6. When the overcurrent control signal SD is low, both NPN transistors Q11 and Q12 are cut off, and the green LED diode DS6 is lit; when the overcurrent control signal SD is high, both NPN transistors Q11 and Q12 are turned on, and the red LED diode DS5 is lit.

[0049] The circuit connection of the above-mentioned load voltage and current display circuit 6 is as follows: the current amplification and comparison control circuit 60 is electrically connected to the current sampling circuit 56, the overcurrent protection circuit 61 is electrically connected to the current amplification and comparison control circuit 60, the overcurrent protection circuit 61 is electrically connected to the single-channel PWM generation circuit 51, the overcurrent protection status display circuit 62 is electrically connected to the output terminal of the second low-voltage rectifier and filter circuit 28, and the overcurrent protection status display circuit 62 is electrically connected to the current amplification and comparison control circuit 60.

[0050] This high-power, wide-range adjustable DC linear regulated power supply has the advantages of wide voltage regulation range, high power, small size, high power factor, and fast frequency response.

[0051] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A high-power, wide-range adjustable DC linear regulated power supply, comprising a switching power supply input circuit, an auxiliary switching power supply circuit, a power factor compensation boost circuit, and a switching power supply isolation power conversion circuit; The switching power supply circuit includes a short-circuit protection circuit, a first EMI circuit, a second EMI circuit, a first rectifier and filter circuit, and a second rectifier and filter circuit. The input terminal of the short-circuit protection circuit is connected to the mains power. The output terminal of the short-circuit protection circuit is electrically connected to the input terminals of the first EMI circuit and the second EMI circuit, respectively. The output terminal of the first EMI circuit is electrically connected to the input terminal of the first rectifier and filter circuit, which outputs a +300V DC voltage. The output terminal of the second EMI circuit is electrically connected to the input terminal of the second rectifier and filter circuit, which outputs a +300V DC voltage. The output terminal of the second rectifier and filter circuit is electrically connected to a power factor compensation boost circuit, which outputs a 390V DC voltage. The auxiliary switching power supply circuit includes a switching power supply chip, an output power adjustment circuit, a line voltage detection circuit, a drain clamping circuit, an auxiliary power supply rectifier and filter circuit, an energy storage switching transformer, a precision optocoupler feedback voltage regulation control circuit, a first low-voltage rectifier and filter circuit, and a second low-voltage rectifier and filter circuit. The output terminal of the first rectifier and filter circuit is electrically connected to the energy storage switching transformer, the input terminal of the line voltage detection circuit, the input terminal of the output power adjustment circuit, and the output terminal of the drain clamping circuit, respectively. The switching power supply chip is connected to the output terminal of the line voltage detection circuit, the input terminal of the drain clamping circuit, the output terminal of the output power adjustment circuit, and the precision optocoupler feedback voltage regulation control circuit, respectively. The circuit is electrically connected, and the input terminal of the drain clamping circuit is also electrically connected to the input terminal of the energy storage switch transformer. The output terminal of the energy storage switch transformer is electrically connected to the input terminals of the first low-voltage rectifier filter circuit, the second low-voltage rectifier filter circuit, and the auxiliary power supply rectifier filter circuit, respectively. The output terminal of the first low-voltage rectifier filter circuit outputs a non-isolated +13.3V DC voltage, and the output terminal of the second low-voltage rectifier filter circuit outputs an isolated +12V DC voltage. The output terminal of the second low-voltage rectifier filter circuit is electrically connected to the precision optocoupler feedback voltage regulation control circuit, and the output terminal of the auxiliary power supply rectifier filter circuit is electrically connected to the precision optocoupler feedback voltage regulation control circuit. The switching power supply isolated power conversion circuit includes a dual-channel PWM signal generation circuit, an H-bridge drive circuit, a power isolation conversion circuit, a third rectifier and filter circuit, a precision optocoupler isolation voltage regulation control circuit, and an optocoupler isolation overcurrent control circuit. The output terminal of the power factor compensation boost module is electrically connected to the input terminal of the power isolation conversion circuit. The output terminal of the power isolation conversion circuit is electrically connected to the input terminal of the third rectifier and filter circuit. The output terminal of the power isolation conversion circuit is also electrically connected to the input terminal of the optocoupler isolation overcurrent control circuit and the output terminal of the H-bridge drive circuit. The output terminal of the third rectifier and filter circuit is also electrically connected to the input terminal of the precision optocoupler isolation voltage regulation control circuit. The output terminals of the optocoupler isolation overcurrent control circuit, the H-bridge drive circuit, and the precision optocoupler isolation voltage regulation control circuit are respectively electrically connected to the dual-channel PWM signal generation circuit. The first low-voltage rectifier and filter circuit is respectively electrically connected to the dual-channel PWM signal generation circuit and the H-bridge drive circuit, providing power to the dual-channel PWM signal generation circuit and the H-bridge drive circuit. Its features are: It also includes a voltage and current controllable BUCK circuit and a load voltage and current display circuit; The voltage and current controllable BUCK circuit includes a startup circuit, a single-channel PWM generation circuit, a single-supply bootstrap level transfer isolation drive circuit, a BUCK circuit, an LC filter circuit, an adjustable output voltage sampling circuit, an output current sampling circuit, a voltage display circuit, and a current display circuit. The startup circuit, the single-supply bootstrap level transfer isolation drive circuit, and the BUCK circuit are electrically connected to the output terminal of the third rectifier filter circuit. The startup circuit is electrically connected to the single-channel PWM generation circuit. The single-channel PWM generation circuit is also electrically connected to the single-supply bootstrap level transfer isolation drive circuit, the adjustable output voltage sampling circuit, and the overcurrent protection circuit. The BUCK circuit is electrically connected to the adjustable output voltage sampling circuit and also electrically connected to the input terminal of the LC filter circuit. The output current sampling circuit is electrically connected to the output terminal of the LC filter circuit. The current display circuit is electrically connected to the output current sampling circuit, and the voltage display circuit is electrically connected to the output terminal of the LC filter circuit. The single-supply bootstrap level transfer isolation drive circuit includes resistors R2, R3, R5, R11, R12, electrolytic capacitor C3, ceramic capacitor C9, Zener diode DS1, diode D1, diode D3, optocoupler IC3, PNP transistor Q2, and PNP transistor Q3. The positive terminal of the optocoupler IC3 is electrically connected to the single-channel PWM generation circuit through resistor R5. The ceramic capacitor C9 is connected in parallel with resistor R5. The negative terminal of the optocoupler IC3 is grounded through resistor R11. The first terminal of resistor R2 and the base of PNP transistor Q2 are electrically connected to the collector of optocoupler IC3, respectively. The emitter of PNP transistor Q2 is electrically connected to the first terminal of resistor R3. The second terminals of resistor R2, R3, and the positive terminal of electrolytic capacitor C3 are electrically connected to the negative terminal of diode D1, respectively. The positive terminal of diode D1 is electrically connected to the startup circuit. The emitter of optocoupler IC3, the base of PNP transistor Q3, the positive terminal of diode D3, and the first terminal of resistor R12 are electrically connected to the collector of PNP transistor Q2. The negative terminal of Zener diode DS1 and the emitter of PNP transistor Q3 are electrically connected to the negative terminal of diode D3. The negative terminal of electrolytic capacitor C3, the positive terminal of Zener diode DS1, the collector of PNP transistor Q3, and the second terminal of resistor R12 are electrically connected to the BUCK circuit. The load voltage and current display circuit includes a current amplification and comparison control circuit, an overcurrent protection circuit, and an overcurrent protection status display circuit. The current amplification and comparison control circuit is electrically connected to the current sampling circuit. The overcurrent protection circuit is electrically connected to the current amplification and comparison control circuit and to a single-channel PWM generation circuit. The overcurrent protection status display circuit, the current amplification and comparison control circuit, and the voltage display circuit are all electrically connected to the output terminal of the second low-voltage rectifier and filter circuit. The overcurrent protection status display circuit is also electrically connected to the current amplification and comparison control circuit.

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