Boost type digital adjustable high-voltage isolation power supply

Abstract

The invention discloses a Boost type digital adjustable high-voltage isolation power supply, which belongs to the technical field of high-voltage isolation power supplies, and comprises an isolation voltage control unit, a low-voltage isolation power supply and a boost unit, the isolation voltage control unit is used for generating an isolation control signal, the low-voltage isolation power supply is used for generating an isolated low-voltage power supply, and the boost unit is used for realizing stable closed-loop output through a PWM controller and a feedback circuit according to the isolation control signal and the low-voltage power supply based on a topological structure of a Boost circuit. The isolation side is converted from low voltage to high voltage. According to the invention, a simple Boost topological structure is used, a digital adjustable function is realized under a low-power isolation high-voltage occasion, and through the establishment of the PWM controller and discrete devices, the circuit has the characteristics of low cost, high reliability, simple structure, strong configurability and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of high-voltage isolated power supplies, and in particular to a Boost-type digitally adjustable high-voltage isolated power supply. Background Art

[0002] Low-power, high-voltage isolated power supplies are widely used in analytical instruments, medical equipment, industrial control and testing, and other fields. In industrial automation and mass spectrometry, it is necessary to achieve the function of outputting adjustable high voltage in different application scenarios. In medical equipment, not only the high-voltage power supply is required to be stable and reliable, but also reliable electrical isolation performance is required.

[0003] To achieve reliable output and high electrical isolation, off-the-shelf power modules are often used. However, these modules are expensive and have limited application scenarios. Therefore, a boost-type digitally adjustable high-voltage isolated power supply is proposed. Through flexible component selection, a highly reliable isolated adjustable power supply is achieved at low cost. Summary of the Invention

[0004] The technical problem to be solved by the present invention is how to solve the problems of high cost and single application scenario of directly using finished power modules, and provides a Boost type digitally adjustable high-voltage isolated power supply.

[0005] The present invention solves the above-mentioned technical problems through the following technical solutions. The present invention includes an isolation voltage control unit, a low-voltage isolation power supply and a boost unit; the isolation voltage control unit is used to generate an isolation control signal, the low-voltage isolation power supply is used to generate an isolated low-voltage power supply, and the boost unit is used to achieve a stable closed-loop output through a PWM controller and a feedback circuit according to the isolation control signal, the low-voltage power supply, and the topology of the Boost circuit, thereby converting the isolation side from low voltage to high voltage.

[0006] Furthermore, the isolation voltage control unit includes a main control module, a digital signal isolator and a DAC. The main control module generates a digital signal corresponding to the target voltage, transmits it to the isolation side through the digital signal isolator, and generates a set voltage signal Vset through the DAC on the isolation side.

[0007] Furthermore, the main control module is MCU, DSP or FPGA.

[0008] Furthermore, the low-voltage isolated power supply includes an isolated power supply module and a filtering and voltage-stabilizing circuit. The VDD voltage is input on the non-isolated side, and after passing through the isolated power supply module, an isolated low-voltage power supply VD_ISO is generated on the isolated side, and then the VD_ISO power supply is converted into VA_ISO power supply through the filtering and voltage-stabilizing circuit.

[0009] Furthermore, the isolated power supply module is a DC-DC module, and the filtering and voltage stabilizing circuit includes an LC low-pass filtering circuit and an LDO, the LC low-pass filtering circuit is used to filter out high-frequency switching noise, and the LDO is used to filter out low-frequency noise.

[0010] Furthermore, the boost unit includes a PWM controller U1, a Boost circuit and a feedback circuit. The PWM controller U1 is provided with a PWM output terminal OUT, a feedback voltage terminal FB and a current sampling terminal CS, wherein the PWM output terminal OUT and the current sampling terminal CS are both electrically connected to the Boost circuit, the feedback voltage terminal FB is electrically connected to the feedback circuit, and the feedback circuit is also connected to the output terminal of the Boost circuit.

[0011] Furthermore, the Boost circuit includes a matching resistor R1, a current sampling resistor R2, a switch tube Q1, an inductor L1, a diode D1 and an output capacitor C1. The matching resistor R1 is connected in series between the PWM output terminal OUT and the gate of the switch tube Q1. One end of the current sampling resistor R2 is grounded, and the other end is connected to the current sampling terminal CS and the source of the switch tube Q1. One end of the inductor L1 is connected to the VD_ISO power supply terminal, and the other end is connected to the drain of the switch tube Q1. The drain of the switch tube Q1 is also connected to the output terminal Vout through the diode D1. One end of the output capacitor C1 is connected to the output terminal Vout, and the other end is grounded.

[0012] Furthermore, the feedback circuit includes a feedback follower amplifier U3, a feedback voltage conditioning amplifier U2, a feedback resistor R3, a feedback resistor R8, a feedback compensation capacitor C2, a feedback output resistor R4, a feedback resistor R5, a feedback resistor R6, a resistor R7, and a resistor R9. The non-inverting input terminal of the feedback follower amplifier U3 is connected to one end of the feedback resistor R3 and the feedback resistor R8 respectively, the other end of the feedback resistor R3 is connected to the output terminal Vout, the other end of the feedback resistor R8 is grounded, and the inverting input terminal of the feedback follower amplifier U3 is connected to its output terminal Vout. The output of the feedback follower amplifier U3 is connected to the non-inverting input of the feedback voltage conditioning amplifier U2 through the resistor R7. The inverting input of the feedback voltage conditioning amplifier U2 is grounded through the feedback resistor R6. The feedback compensation capacitor C2 and the feedback resistor R5 are connected in parallel between the inverting input and output of the feedback voltage conditioning amplifier U2. The output of the feedback voltage conditioning amplifier U2 is also connected to the feedback voltage terminal FB through the feedback output resistor R4. The Vset signal is input to the non-inverting input of the feedback voltage conditioning amplifier U2 through the resistor R9.

[0013] Furthermore, the feedback follows the output voltage V OUT3 The calculation formula is:

[0014]

[0015] Among them, V IN2+ The voltage at the non-inverting input of the feedback voltage conditioning amplifier U2 is V SET is the target voltage corresponding to the Vset signal, and R7 and R9 are the resistance values ​​of resistors R7 and R9.

[0016] Furthermore, the calculation formula of the output voltage Vout of the Boost circuit is:

[0017]

[0018] Among them, R3 and R8 are the resistance values ​​of the feedback resistor R3 and the feedback resistor R8.

[0019] Compared with the existing technology, the present invention has the following advantages: the Boost-type digitally adjustable high-voltage isolated power supply uses a simple Boost-type topology to achieve digital adjustable function in low-power isolated high-voltage situations. It is built through a PWM controller and discrete components, and has the characteristics of low cost, high reliability, simple structure and strong configurability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic block diagram of the structure of a digitally adjustable high-voltage isolated power supply in an embodiment of the present invention;

[0021] Figure 2 2 is a schematic structural diagram of an isolation voltage control unit according to an embodiment of the present invention;

[0022] Figure 3 1 is a schematic structural diagram of a low-voltage isolated power supply according to an embodiment of the present invention;

[0023] Figure 4 is a circuit schematic diagram of a boost unit in an embodiment of the present invention;

[0024] Figure 5 4 is a circuit diagram of a high-voltage isolated power supply in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process. However, the protection scope of the present invention is not limited to the following embodiment.

[0026] This embodiment provides a technical solution: a boost-type digitally adjustable high-voltage isolated power supply, comprising three modules: an isolation voltage control unit, a low-voltage isolated power supply, and a boost unit;

[0027] The isolation voltage control unit is used to generate the isolation control signal, mainly including the main control module, digital signal isolator, and DAC;

[0028] The main control module is implemented by a microcontroller, which generates a digital signal corresponding to the target voltage and transmits it to the isolation side through a digital signal isolator. On the isolation side, a DAC is used to generate a set voltage signal Vset.

[0029] In this embodiment, the microcontroller can be a general-purpose MCU, DSP or FPGA, and the digital signal isolator is mainly used to isolate the digital signal generated by the low-voltage side microcontroller from the digital signal of the high-voltage side DAC; the DAC is used to generate a Vset signal on the high-voltage side, which is used to control the boost unit to generate the set target high voltage. The number of bits of the DAC is related to the resolution of the adjustable high-voltage isolated power supply. If the target voltage needs to reach a maximum of 400V and the setting accuracy is required to be 0.1V, at least 4000LSB is required, and theoretically 12 bits can be used; if the required setting accuracy is 0.05V, a 14-bit or 16-bit DAC needs to be selected.

[0030] The isolated voltage control unit is not limited to the above-mentioned technical implementation scheme. The ultimate goal is to generate an isolated and adjustable Vset signal. It can also generate an analog signal on the low-voltage side through the main control module and DAC, and then generate a Vset signal in the high-voltage area through an analog signal isolator (such as the NSI1311 chip).

[0031] A low-voltage isolated power supply is used to generate an isolated low-voltage power supply. This can be generated using an isolated power supply module, which is typically isolated internally via a transformer. The VDD voltage is input to the non-isolated side, and after passing through the isolated power supply module, the isolated low-voltage power supply VD_ISO is generated on the isolated side. Because the isolated voltage module and the boost circuit of the boost unit generate some switching ripple, to ensure more stable power supply for the analog feedback circuit in the boost unit, the isolated low-voltage power supply VD_ISO can be low-pass filtered (e.g., with an LC filter) to remove high-frequency switching noise. Furthermore, an LDO can be used to stabilize the VD_ISO power supply to the VA_ISO power supply, effectively filtering out low-frequency noise. In applications where voltage stability is less critical, the LDO or LC filtering circuit can be omitted.

[0032] Low-voltage isolated power supply is not limited to the use of isolated power supply modules. Its purpose is to generate a low-voltage power supply on the isolated side, which can also be achieved through a flyback circuit.

[0033] The boost unit is a circuit module used to convert the isolation side from low voltage to high voltage. Based on the topology of the Boost circuit, it achieves a stable closed-loop output through a PWM controller and feedback circuit.

[0034] The boost unit mainly includes PWM controller U1, matching resistor R1, current sampling resistor R2, switch tube Q1, inductor L1, diode D1, output capacitor C1, feedback resistors R3, R8, feedback follower op amp U3, feedback voltage conditioning op amp U2 and surrounding resistors R5, R6, R7, R9, feedback compensation capacitor C2, and feedback output resistor R4.

[0035] PWM controller U1 adjusts the PWM duty cycle at the output (OUT) based on the signal at the feedback voltage (FB), thereby regulating the output voltage Vout. When using the UCC2801 chip, PWM controller U1 also includes some simple peripheral circuits, including frequency adjustment and some internal compensation circuits. The specific switching frequency must be matched with the parameters of inductor L1 and capacitor C1 to meet the ripple requirements of the output voltage Vout.

[0036] Resistor R1 is connected in series between the PWM output terminal (OUT terminal) of the PWM controller U1 and the gate of the switch tube Q1 to match the output impedance and reduce the ringing amplitude generated during the switching process. It can also reduce the switching speed of the switch tube Q1 and reduce external EMC interference. The value of this resistor should normally be less than 100Ω, otherwise it will cause the switch tube Q1 to turn on too slowly, increase the switching loss, and increase the heat generated by Q1. The switch tube Q1 is the switch tube of the Boost circuit and requires an NMOS power tube. Resistor R2 is used to sample the current when the switch tube Q1 is turned on. The PWM controller U1 detects the voltage at the resistor R2 terminal cycle by cycle. When the voltage reaches the overcurrent threshold built into the chip, the output of the OUT terminal is immediately turned off to achieve the overcurrent protection function. Inductor L1 is the energy storage inductor of the Boost circuit. When the switch tube Q1 is disconnected, the diode D1 provides a freewheeling circuit for the inductor L1. When the switch tube Q1 is turned on, the reverse phase of the diode is used to The cutoff characteristics isolate the Vout terminal voltage. Diode D1 can use a fast recovery diode. Since this application is a boost circuit, high output voltages require this diode to have sufficient withstand voltage. Capacitor C1 is the output capacitor of the boost circuit. The capacitance of this capacitor should be selected based on the output load current and ripple requirements. Similar to diode D1, capacitor C1 also needs to have a high withstand voltage that meets the output voltage requirements. If a ceramic capacitor is used for C1, the capacitor withstand voltage parameters must meet a 50% derating requirement due to the DC bias characteristics of ceramic capacitors. R3 and R8 are the feedback resistors. To meet the withstand voltage requirements, R3 needs to use a large package, typically 1206 (package size) or larger. The withstand voltage of a 1206 package resistor is generally around 200V (resistors with the same package but different models and materials have different withstand voltage parameters; refer to the specific datasheet). Higher withstand voltage requirements can be achieved by connecting multiple 1206 resistors in series. U3 is a precision operational amplifier. To achieve impedance matching between the resistor feedback loop and the voltage conditioning loop, U3 is used to form a follower.

[0037] The feedback voltage conditioning op amp U2, along with its surrounding resistors R5, R6, R7, and R9, feedback compensation capacitor C2, and feedback output resistor R4, collectively implement feedback control of the target voltage. Resistor R9 is connected to Vset on one end and to the non-inverting input of U2 on the other. It is also connected to one end of resistor R7, the other end of which is connected to the output of U3. Because the voltage at U3's output is proportional to Vout, resistors R7 and R9 establish a correlation between Vset and Vout. By setting different Vset voltages, the output Vout voltage is obtained. Resistors R5 and R6 form U2's feedback network. By setting different resistance values, a non-inverting amplifier circuit with different amplification ratios is implemented.

[0038] When the PWM controller U1 uses the UCC2801 chip, the voltage at its feedback voltage terminal FB is a constant value of 2.5V. Resistor R4 is connected in series between the output terminal of U2 and the feedback voltage terminal FB of U1 to prevent the output terminal of U2 from directly driving the capacitive load of the feedback voltage terminal FB of U1 and causing oscillation of U2. Feedback resistors R5 and R6 together realize the feedback loop of the non-inverting amplifier circuit composed of U2, and the amplification ratio G=1+R5 / R6; capacitor C2 is connected across the inverting input and output terminals of U2 to realize the phase compensation of U2; resistor R9 is connected to the output terminal of DAC, and resistor R7 is connected to the output terminal of U3. Since the non-inverting input of U2 is high impedance, the output current of U3 will only flow to the output terminal of DAC through resistors R7 and R9. Under the condition of stable feedback loop, since the output voltage of U2 is connected to the feedback voltage terminal FB of U1, the voltage V at the feedback voltage terminal FB of U1 is FB The voltage at the inverting input of U2 is V IN2- Equal to V FB *R6 / (R5+R6), U2’s non-inverting input voltage V IN2+ Also equal to V FB *R6 / (R5+R6), the DAC output voltage Vset is a known set voltage. Using Kirchhoff's current law, the voltage at the output of U3 can be calculated as:

[0039]

[0040] Because U3 is a follower, the voltage at the non-inverting input of U3 is equal to Vout3. Then, the voltage value of Vout can be calculated through the voltage divider network of R3 and R8. The calculation formula is:

[0041]

[0042] When U1 uses the UCC2801 chip, the chip has a built-in overcurrent detection threshold V at the CS end. CS_TH =1V, when the voltage across R2 exceeds 1V, the PWM output OUT port will be disabled within 100nS, thus achieving the overcurrent protection function. Assuming the saturation current of inductor L1 is I L1_SAT =3A, under the condition that the overcurrent capacity of Q1 is greater than 3A, in order to prevent the inductor L1 from saturating, the resistor R2 needs to be greater than 0.33 ohms, and the calculation formula is R3 = V CS_TH / I L1_SAT .

[0043] In summary, the Boost digitally adjustable high-voltage isolated power supply of the above embodiment uses a simple Boost topology to achieve digital adjustable function in low-power isolated high-voltage situations. It is built through a PWM controller and discrete components and has the characteristics of low cost, high reliability, simple structure and strong configurability.

[0044] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A Boost type digital adjustable high voltage isolated power supply, characterized in that: include: Isolation voltage control unit, low voltage isolation power supply and boost unit; The isolation voltage control unit is used to generate an isolation control signal, the low-voltage isolated power supply is used to generate an isolated low-voltage power supply, and the boost unit is used to achieve a stable closed-loop output through a PWM controller and a feedback circuit based on the isolation control signal, the low-voltage power supply, and the topology of the Boost circuit, thereby converting the isolation side from low voltage to high voltage.

2. The Boost type digital adjustable high-voltage isolated power supply according to claim 1, characterized in that: The isolation voltage control unit includes a main control module, a digital signal isolator and a DAC. The main control module generates a digital signal corresponding to the target voltage, transmits it to the isolation side through the digital signal isolator, and generates a set voltage signal Vset through the DAC on the isolation side.

3. The Boost type digitally adjustable high-voltage isolated power supply according to claim 2, characterized in that: The main control module is MCU, DSP or FPGA.

4. The Boost digital adjustable high-voltage isolated power supply according to claim 2, characterized in that: The low-voltage isolated power supply includes an isolated power supply module and a filtering and voltage-stabilizing circuit. The VDD voltage is input on the non-isolated side. After passing through the isolated power supply module, an isolated low-voltage power supply VD_ISO is generated on the isolated side. The VD_ISO power supply is then converted into VA_ISO power supply through the filtering and voltage-stabilizing circuit.

5. The Boost digitally adjustable high-voltage isolated power supply according to claim 4, characterized in that: The isolated power supply module is a DC-DC module, and the filtering and voltage stabilizing circuit includes an LC low-pass filtering circuit and an LDO. The LC low-pass filtering circuit is used to filter out high-frequency switching noise, and the LDO is used to filter out low-frequency noise.

6. The Boost digitally adjustable high-voltage isolated power supply according to claim 5, characterized in that: The boost unit includes a PWM controller U1, a Boost circuit and a feedback circuit. The PWM controller U1 is provided with a PWM output terminal OUT, a feedback voltage terminal FB and a current sampling terminal CS, wherein the PWM output terminal OUT and the current sampling terminal CS are both electrically connected to the Boost circuit, the feedback voltage terminal FB is electrically connected to the feedback circuit, and the feedback circuit is also connected to the output terminal of the Boost circuit.

7. The Boost digitally adjustable high-voltage isolated power supply according to claim 6, characterized in that: The Boost circuit includes a matching resistor R1, a current sampling resistor R2, a switch tube Q1, an inductor L1, a diode D1 and an output capacitor C1. The matching resistor R1 is connected in series between the PWM output terminal OUT and the gate of the switch tube Q1. One end of the current sampling resistor R2 is grounded, and the other end is connected to the current sampling terminal CS and the source of the switch tube Q1. One end of the inductor L1 is connected to the VD_ISO power supply terminal, and the other end is connected to the drain of the switch tube Q1. The drain of the switch tube Q1 is also connected to the output terminal Vout through the diode D1. One end of the output capacitor C1 is connected to the output terminal Vout, and the other end is grounded.

8. The Boost digitally adjustable high-voltage isolated power supply according to claim 7, characterized in that: The feedback circuit includes a feedback follower amplifier U3, a feedback voltage conditioning amplifier U2, a feedback resistor R3, a feedback resistor R8, a feedback compensation capacitor C2, a feedback output resistor R4, a feedback resistor R5, a feedback resistor R6, a resistor R7, and a resistor R9. The non-inverting input terminal of the feedback follower amplifier U3 is connected to one end of the feedback resistor R3 and the feedback resistor R8 respectively, the other end of the feedback resistor R3 is connected to the output terminal Vout, the other end of the feedback resistor R8 is grounded, and the inverting input terminal of the feedback follower amplifier U3 is connected to its output terminal. At the same time, the output end of the feedback follower op amp U3 is connected to the non-inverting input end of the feedback voltage conditioning op amp U2 through the resistor R7, the inverting input end of the feedback voltage conditioning op amp U2 is grounded through the feedback resistor R6, the feedback compensation capacitor C2 and the feedback resistor R5 are connected in parallel between the inverting input end and the output end of the feedback voltage conditioning op amp U2, and the output end of the feedback voltage conditioning op amp U2 is also connected to the feedback voltage end FB through the feedback output resistor R4. The Vset signal is input to the non-inverting input end of the feedback voltage conditioning op amp U2 through the resistor R9.

9. The Boost digitally adjustable high-voltage isolated power supply according to claim 8, characterized in that: The feedback follows the output voltage V of the op amp U3 OUT3 The calculation formula is: Among them, V IN2+ The voltage at the non-inverting input of the feedback voltage conditioning amplifier U2 is V SET is the target voltage corresponding to the Vset signal, and R7 and R9 are the resistance values ​​of resistors R7 and R9.

10. The Boost type digitally adjustable high-voltage isolated power supply according to claim 9, characterized in that: The calculation formula of the output voltage Vout of the Boost circuit is: Among them, R3 and R8 are the resistance values ​​of the feedback resistor R3 and the feedback resistor R8.

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