Low-ripple high-voltage circuit based on discrete components

Abstract

A low-ripple high-voltage circuit formed based on discrete components belongs to the field of linear power supplies, and is characterized by comprising an oscillation control circuit, a voltage doubling rectifying circuit and a voltage stabilizing circuit which are connected in sequence, an MOS (Metal Oxide Semiconductor) tube is arranged between the oscillation control circuit and the voltage doubling rectifying circuit; the MOS tube is connected with the input end of the circuit; a filter capacitor is arranged between the voltage doubling rectifying circuit and the voltage stabilizing circuit; the oscillation control circuit is a symmetrical multi-harmonic oscillation control circuit which is composed of two phase inverters and has no external input; and the voltage stabilizing circuit is connected with the circuit output end. Discrete components are adopted to form the oscillation control circuit, the half-wave four-order voltage doubling rectifying circuit and the series voltage stabilizing circuit, then the low-ripple high-voltage circuit is formed and used for a power supply system, the cost is low due to the fact that the discrete components are adopted, meanwhile, a triode works in an amplification area, the performance that the output ripple of the circuit is small is met, the structure is simple, and cost is low. The high-voltage low-ripple power supply can be applied to high-voltage low-ripple power supply application occasions and is suitable for popularization and application.

Description

Technical Field

[0001] The utility model belongs to the field of linear power supplies, and in particular relates to a low-ripple high-voltage circuit composed of discrete components. Background Art

[0002] In the current common power supply systems, most of the devices used in the power supply system are integrated devices, using a cascade structure composed of MOS tubes or triodes. In order to increase efficiency, the tubes will operate in the saturation region and the cutoff region. Therefore, the switching ripple is larger than that of the tubes working in the linear region. As a result, the power supply system using integrated devices has the problem of high price and large ripple, and there is also the problem of not meeting the application of high voltage and low ripple power supply. Summary of the Invention

[0003] The utility model aims to solve the above problems and provides a low ripple high voltage circuit composed of discrete components.

[0004] The low-ripple high-voltage circuit based on discrete components of the present invention includes an oscillation control circuit, a voltage-doubling rectifier circuit, and a voltage-stabilizing circuit, which are connected in sequence. A MOS transistor is provided between the oscillation control circuit and the voltage-doubling rectifier circuit; the MOS transistor is connected to the circuit input end; a filter capacitor is provided between the voltage-doubling rectifier circuit and the voltage-stabilizing current; the oscillation control circuit is a symmetrical multivibrator control circuit without external input, which is composed of two inverters; and the voltage-stabilizing circuit is connected to the circuit output end.

[0005] The circuit input terminal is connected to an external power supply to power the oscillation control circuit. The oscillation control circuit generates a square wave signal with a fixed frequency. The square wave signal controls the switch of the MOS tube, continuously charging the charge pump circuit composed of diodes and capacitors in the back-end voltage doubler rectifier circuit, and raising the voltage to a preset high voltage output. After the output high voltage is stabilized by the series voltage regulator circuit, a stable high voltage is output for use by the back-end circuit.

[0006] Furthermore, the low ripple high voltage circuit based on discrete components of the present invention comprises a voltage regulator circuit including a voltage regulator tube, a transistor Q1 and a current limiting resistor R1; the voltage regulator tube includes two, namely a first voltage regulator tube D9 and a second voltage regulator tube D10; the current limiting resistor R1, the first voltage regulator tube D9 and the second voltage regulator tube D10 are arranged in series; the base B of the transistor Q1 serves as the input stage, and the emitter E serves as the output stage; the collector C serves as the common electrode; one end of the current limiting resistor R1 is connected to the aforementioned voltage doubling rectifier circuit, and the other end is connected to the negative electrode of the voltage regulator tube D9; the positive electrode of the second voltage regulator tube D10 is grounded; the negative electrode of the first voltage regulator tube D9 is connected to the base B of the transistor Q1; the base B of the transistor Q1 is connected to the filter capacitor C12; the emitter E of the transistor Q1 is connected to the circuit output end; the collector C of the transistor Q1 is connected to the aforementioned voltage doubling rectifier circuit after passing through the filter capacitors C8 and C9 arranged in parallel.

[0007] The core of the voltage-stabilizing circuit is a transistor with a common collector connection. The input is the base and the output is the emitter, also called an emitter follower. The output follows the changes in the input. Theoretically, the output voltage = input voltage - 0.7V, and the base voltage is composed of two Zener diodes connected in series to form a reference power supply. This power supply does not change with changes in the collector voltage. Through the current-limiting resistor, the current passing through the Zener diode is guaranteed to be within a certain range, and the output voltage is stable.

[0008] Furthermore, the low ripple high voltage circuit based on discrete components of the present invention, the oscillation control circuit includes an inverter U1_A, an inverter U1_B, a capacitor C13, a capacitor C14, a resistor R3, and a resistor R4; the inverter U1_A is connected in parallel with the resistor R3, and the inverter U1_B is connected in parallel with the resistor R4; the inverter U1_A, the capacitor C13, and the inverter U1_B are connected in series; one end of the capacitor C14 is connected to the input of the inverter U1_A, and the other end is connected to the output of the inverter U1_B; the output of the inverter U1_B is connected to the aforementioned MOS tube after passing through the current limiting resistor R5.

[0009] The oscillation control circuit is composed of two inverters. The MOS tube is the control circuit. The symmetrical multivibrator control circuit has no external input. After power is applied, a small interference is generated on the input end of the inverter. Through positive feedback, the small signal is amplified. The symmetrical R and C make the time of entering the two transient states consistent. Therefore, the duty cycle of the output pulse signal is 50%, and the frequency is determined by R and C. This pulse waveform is applied to the gate of the MOS tube and compared with the gate threshold voltage of the MOS tube. When the high level of the pulse is greater than the threshold voltage, the tube is turned on and the drain output voltage is 0. When the low level of the pulse is less than the threshold voltage, the tube is turned off and the drain output voltage is the same as the external power supply voltage connected to the input end of the circuit.

[0010] Furthermore, the low ripple high voltage circuit based on discrete components of the present invention, the voltage doubler rectifier circuit is a half-wave fourth-order voltage doubler rectifier circuit; the half-wave fourth-order voltage doubler rectifier circuit includes diodes D1 to D8 and capacitors C1 to C7; the diodes D1 to D8 are arranged in parallel; the cathode of the diode D1 is connected to the anode of the diode D2, the anode of the diode D1 is connected to the cathode of the diode D2 through the capacitor C1, and the anode of D1 is grounded; the diode D1 is connected to the aforementioned MOS tube through the capacitor C15; the anode of the diode D2 is connected to the cathode of the diode D3 through the capacitor C2, and the cathode of the diode D2 is connected to the anode of the diode D3; the anode of the diode D3 is connected to the cathode of the diode D4 through the capacitor C3, and the diode The cathode of D3 is connected to the anode of diode D4; the anode of diode D4 is connected to the cathode of diode D5 via capacitor C4; the cathode of diode D4 is connected to the anode of diode D5, and the cathode of diode D5 is connected to the anode of diode D6; the anode of diode D5 is connected to the cathode of diode D6 via capacitor C5, and the cathode of diode D6 is connected to the anode of diode D7; the anode of diode D6 is connected to the cathode of diode D7 via capacitor C6, and the cathode of diode D6 is connected to the anode of diode D7; the anode of diode D7 is connected to the cathode of diode D8 via capacitor C7, and the cathode of diode D7 is connected to the anode of diode D8; the cathode of diode D8 is connected to the aforementioned current-limiting resistor R1.

[0011] The half-wave fourth-order voltage doubler rectifier circuit is composed of a diode and a capacitor. It utilizes the energy storage of the capacitor and the unidirectional conductivity of the diode. When a positive pulse occurs, the corresponding capacitor is charged. When the input is 0, it is equivalent to the transfer of the capacitor voltage, that is, the capacitor charged by the positive pulse is equivalent to a voltage source, discharging the capacitor of the subsequent stage, while the capacitor of the subsequent stage is charged. The final voltage output is the sum of the four capacitor voltages, which is equal to 4 times the input pulse voltage amplitude.

[0012] The low-ripple high-voltage circuit based on discrete components of the utility model adopts discrete components to form an oscillation control circuit, a half-wave fourth-order voltage doubler rectifier circuit, and a series voltage regulator circuit, thereby forming a low-ripple high-voltage circuit for a power supply system. Since the discrete components adopted are low in cost, and the transistors operate in the amplification region to meet the circuit output ripple performance, the structure is simple, and the application occasions of high-voltage low-ripple power supplies can be met, and the utility model is suitable for popularization and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic diagram of a low ripple high voltage circuit based on discrete components according to an embodiment of the present invention. DETAILED DESCRIPTION

[0014] The low ripple high voltage circuit based on discrete components of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0015] This embodiment discloses a low ripple high voltage circuit based on discrete components, which is composed of discrete components such as Figure 1 The circuit shown includes inverter U1, diodes D1-D8, non-polarized capacitors C1-C15, voltage regulators D9-D10, resistors R1-R6, transistor Q1, and MOS transistor Q2. The low-ripple, high-voltage circuit based on discrete components consists of three parts: an oscillator control circuit, a half-wave fourth-order voltage doubler rectifier circuit, and a series voltage regulator circuit.

[0016] In this embodiment, the 23V power supply at the circuit input is first converted to 5V using a 78L05 voltage regulator (a common voltage regulator; if the 78L05 is connected to a 23V input, the output is 5V). This 5V voltage is used to power the oscillation control circuit, which generates a fixed-frequency square wave signal. This square wave signal controls the switching of the MOS transistor, continuously charging the charge pump circuit composed of diodes and capacitors in the downstream half-wave fourth-order voltage doubler rectifier circuit, raising the voltage to a preset high output voltage. After being stabilized by the series voltage regulator circuit, the output voltage is approximately 50.3V in this disclosed embodiment for use by the downstream circuitry. The amplitude of the final output voltage is related to the 23V input voltage.

[0017] In the embodiment of the present disclosure, when the low ripple high voltage circuit composed of discrete components is working, the working principle of the oscillation control circuit is as follows: when power is turned on, there is a positive disturbance at the inverter U1_1 pin, the inverter U1_6 pin outputs a low level, the voltage on both sides of the capacitor C13 cannot change suddenly, the inverter U1_3 pin is also a low level, the U1_4 pin is a high level, the voltage on both sides of the capacitor C14 cannot change suddenly, the inverter U1_1 pin is also a high level superimposed on the positive disturbance, the left side of the capacitor C13 is a low level, and the right side is also a low level. The high level of the inverter U1_4 charges the right plate of the capacitor C13 through the resistor R4, and the voltage difference across the capacitor C13 slowly increases. At the same time, the left side of the capacitor C14 is the disturbance voltage superimposed on the high level, and the right side is a high level. The capacitor C14 discharges through the resistor R3, and the voltage difference across the capacitor C14 slowly decreases, and the circuit enters the first transient state. When the voltage at the inverter U1_3 pin on the right side of capacitor C13 increases to the inverter threshold of 4.5V, inverter U1_4 outputs a low level, the voltage across capacitor C14 cannot change suddenly, inverter U1_1 also becomes a low level, inverter U1_6 is a high level, the voltage on both sides of capacitor C13 cannot change suddenly, inverter U1_3 also becomes a high level superimposed on the voltage exceeding the threshold, the voltage on the right side of capacitor C13 is higher than the threshold voltage than the left side, capacitor C13 discharges through resistor R4, and the voltage difference between the two ends slowly decreases. At the same time, both sides of capacitor C14 are low levels, inverter U1_6 charges the left plate of capacitor C14 through resistor R3, and the circuit enters the second quasi-stable state. When the voltage at the inverter U1_1 pin increases to the inverter threshold of 4.5V, it enters the first quasi-stable state again. This cycle repeats, and the inverter U1_4 pin will output a square wave voltage. Because R3=R4, C13=C14, the circuit is a symmetrical structure. The first quasi-stable state and the second quasi-stable state are maintained for the same time. The duty cycle of the output signal is 50%, and the period is approximately equal to 1.4RC=784ns, that is, 1.27MHz. The output high level range is between 4.3 and 5V. This pulse voltage is applied to Q2. Q2 is an N-channel MOS tube with a gate threshold voltage of 4V. Therefore, when the oscillation control circuit outputs a high level, the MOS tube is turned on and the drain outputs a low level. When the oscillation control circuit outputs a low level, the MOS tube is turned off and the drain outputs a 23V voltage. R5 and R6 are both current-limiting resistors.

[0018] In the embodiment of the present disclosure, the half-wave fourth-order voltage doubler rectifier circuit is composed of 8 diodes D1~D8 and 7 1NF capacitors C1~C7 with a withstand voltage of 100V. The withstand voltage of the diodes and capacitors must be greater than the amplitude of the input pulse voltage. Considering a certain margin and the uniformity of the components, the capacitors are selected with a withstand voltage of 100V, and the diodes are the common model 1N4148 with a withstand voltage of 75V. The diode junction capacitance should be small to ensure that the unidirectional conductivity of the diode is normal at a certain frequency.

[0019] The working principle of the half-wave fourth-order voltage doubler rectifier circuit described in this embodiment is: when the first 23V positive pulse comes, diode D1 is cut off, diode D2 is turned on, and capacitor C1 is charged through diode D2. Ignoring the conduction voltage drop of all diodes, capacitor C1 can theoretically be charged to 23V. When the first 0V level comes, diode D2 is cut off, diode D3 is turned on, capacitor C1 is equivalent to a voltage source, and capacitor C2 is charged through diode D3. Capacitor C2 can theoretically be charged to 23V. When the second 23V positive pulse comes, diode D3 is cut off, diode D2 and diode D4 are turned on, capacitor C2 is equivalent to a voltage source, and the superimposed 23V positive pulse passes through diode D2 and diode D4 to charge capacitor C1 and capacitor C3. Theoretically, capacitor C1 and capacitor C3 can be charged to 23V respectively. When the second 0V level comes, diode D2 and diode D4 are cut off, diode D3 and diode D5 are turned on, capacitor C1 and capacitor C3 are equivalent to two voltage sources, and capacitor C2 and capacitor C4 are charged through diode D3 and diode D5. Theoretically, capacitor C2 and capacitor C4 can be charged to 23V respectively. When the third 23V positive pulse comes, diodes D3 and D5 are cut off, diodes D2, D4, and D6 are turned on, capacitors C2 and C4 are equivalent to voltage sources, and the 23V positive pulse is superimposed, and capacitors C1, C3, and C5 are charged through diodes D2, D4, and D6. Theoretically, capacitors C1, C3, and C5 can be charged to 23V respectively. When the third 0V voltage comes, diodes D2, D4, and D6 are cut off, and diodes D3, D5, and D7 are turned on. Capacitors C1, C3, and C5 are equivalent to voltage sources, and capacitors C2, C4, and C6 are charged through diodes D3, D5, and D7. Theoretically, capacitors C2, C4, and C6 can be charged to 23V. When the fourth 23V positive pulse arrives, diodes D3, D5, and D7 are cut off, while diodes D2, D4, D6, and D8 are turned on. Capacitors C2, C4, and C6 act as voltage sources. The superimposed 23V positive pulse charges capacitors C1, C3, C5, and C7 through diodes D2, D4, D6, and D8. Theoretically, capacitors C1, C3, C5, and C7 can reach 23V. Capacitors C1, C3, C5, and C7 are connected in series, with capacitor C1 on the left being grounded and the rectifier circuit output to the right of capacitor C7. In practice, multiple charging cycles are required to reach 23V for the capacitors. The theoretical final voltage is the sum of the four capacitor voltages = 23 × 4 = 92V. However, in reality, the diodes have voltage drops, and the capacitors have equivalent series resistance. This square pulse may be affected by the charging and discharging of the capacitors, resulting in a certain rise and fall time, similar to a sine wave. Due to these combined effects, the measured output voltage is only maintained at around 65V. C8 and C9 are filter capacitors to ensure the stability of the collector voltage of the subsequent stage.

[0020] The working principle of the series voltage regulator circuit is as follows: D9 is a 24V voltage regulator, D10 is a 27V voltage regulator, and the two voltage regulators are connected in series to stabilize the voltage at 51V. This voltage is applied to the base of Q1, and the C12 capacitor on the base is a filter capacitor to filter the 51V voltage. Q1 is an NPN transistor, and the connection method is common collector, also called emitter follower. The input voltage is the base, and the output voltage is the emitter. The output voltage of this connection method is only related to the input voltage, and the input voltage is provided by the voltage regulator and is stable, so the output voltage is also stable, V E =V B -V BE =V B -0.7=51-0.7=50.3V. The output voltage is determined by the BE voltage of the transistor, V BE =0.7V@I C ≤50mA, so the output voltage is basically stable at 50.3V.

[0021] The transistor in the circuit of this embodiment works in the amplification area, so the output ripple is small. When verifying whether it works in the amplification area, first reverse the output to the input to see if the calculated value is within the normal range of the manual. If it is within the requirements, it works in the linear area. If the load is a 12.1K resistor, The minimum value of the transistor amplification factor is 120. , the current on R1 is equal to the sum of the current of the Zener diode and the base current, , I 稳 = I R1 - I B =1.4 mA -34.6 uA =1.365 mA According to the manual requirements of the voltage regulator, the output voltage is stable when the current is 1mA ~ 5mA, so the assumption is established, the transistor is working in the linear region, and the measured output ripple does not exceed 30mV.

[0022] Therefore, the low-ripple high-voltage circuit based on discrete components described in this embodiment outputs high voltage with small ripple, and all uses discrete components, with the advantages of low cost and fast cycle, and is suitable for applications of high-voltage low-ripple power supplies.

Claims

1. A low ripple high voltage circuit based on discrete components, characterized in that: It includes an oscillation control circuit, a voltage doubling rectifier circuit and a voltage stabilizing circuit which are connected in sequence; A MOS tube is provided between the oscillation control circuit and the voltage doubler rectifier circuit; The MOS tube is connected to the circuit input end; A filter capacitor is provided between the voltage doubling rectifier circuit and the voltage stabilizing circuit; The oscillation control circuit is a symmetrical multivibrator control circuit without external input, which is composed of two inverters; The voltage stabilizing circuit is connected to the circuit output end.

2. The low ripple high voltage circuit based on discrete components according to claim 1, characterized in that: The voltage stabilizing circuit includes a voltage stabilizing tube, a transistor Q1 and a current limiting resistor R1; The voltage regulator tubes include two, namely a first voltage regulator tube D9 and a second voltage regulator tube D10; The current limiting resistor R1, the first voltage regulator tube D9 and the second voltage regulator tube D10 are arranged in series; The base B of the transistor Q1 serves as the input stage, the emitter E serves as the output stage, and the collector C serves as the common electrode; One end of the current limiting resistor R1 is connected to the aforementioned voltage doubling rectifier circuit, and the other end is connected to the negative electrode of the voltage regulator tube D9; The positive electrode of the second voltage-stabilizing tube D10 is grounded; the negative electrode of the first voltage-stabilizing tube D9 is connected to the base B of the transistor Q1; The base B of the transistor Q1 is connected to the filter capacitor C12; The emitter E of the transistor Q1 is connected to the output end of the circuit; The collector C of the transistor Q1 is connected to the voltage doubling rectifier circuit via filter capacitors C8 and C9 connected in parallel.

3. The low ripple high voltage circuit based on discrete components according to claim 2, characterized in that: The oscillation control circuit includes an inverter U1_A, an inverter U1_B, a capacitor C13, a capacitor C14, a resistor R3, and a resistor R4; The inverter U1_A is connected in parallel with the resistor R3, and the inverter U1_B is connected in parallel with the resistor R4; The inverter U1_A, capacitor C13, and inverter U1_B are connected in series; One end of the capacitor C14 is connected to the input of the inverter U1_A, and the other end is connected to the output of the inverter U1_B; The output of the inverter U1_B is connected to the aforementioned MOS tube after passing through the current limiting resistor R5.

4. The low ripple high voltage circuit based on discrete components according to claim 3, characterized in that: The voltage doubler rectifier circuit is a half-wave fourth-order voltage doubler rectifier circuit; The half-wave fourth-order voltage doubler rectifier circuit includes diodes D1 to D8 and capacitors C1 to C7; The diodes D1 to D8 are arranged in parallel; the cathode of the diode D1 is connected to the anode of the diode D2, the anode of the diode D1 is connected to the cathode of the diode D2 via the capacitor C1, and the anode of D1 is grounded; the diode D1 is connected to the aforementioned MOS transistor via the capacitor C15; The anode of the diode D2 is connected to the cathode of the diode D3 via the capacitor C2, and the cathode of the diode D2 is connected to the anode of the diode D3; The anode of the diode D3 is connected to the cathode of the diode D4 via the capacitor C3, and the cathode of the diode D3 is connected to the anode of the diode D4; The anode of the diode D4 is connected to the cathode of the diode D5 through the capacitor C4; the cathode of the diode D4 is connected to the anode of the diode D5, and the cathode of the diode D5 is connected to the anode of the diode D6. The anode of the diode D5 is connected to the cathode of the diode D6 through the capacitor C5, and the cathode of the diode D6 is connected to the anode of the diode D7. The anode of the diode D6 is connected to the cathode of the diode D7 through the capacitor C6, and the cathode of the diode D6 is connected to the anode of the diode D7. The anode of the diode D7 is connected to the cathode of the diode D8 via the capacitor C7, and the cathode of the diode D7 is connected to the anode of the diode D8; The cathode of the diode D8 is connected to the current limiting resistor R1 .

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