CN108429461B - High-voltage power supply circuit - Google Patents
High-voltage power supply circuit Download PDFInfo
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- CN108429461B CN108429461B CN201810230133.6A CN201810230133A CN108429461B CN 108429461 B CN108429461 B CN 108429461B CN 201810230133 A CN201810230133 A CN 201810230133A CN 108429461 B CN108429461 B CN 108429461B
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- 238000005070 sampling Methods 0.000 claims abstract description 90
- 230000003321 amplification Effects 0.000 claims description 9
- 238000003199 nucleic acid amplification method Methods 0.000 claims description 9
- 230000010355 oscillation Effects 0.000 abstract description 15
- 230000001105 regulatory effect Effects 0.000 abstract description 5
- 230000002829 reductive effect Effects 0.000 description 9
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- 239000003990 capacitor Substances 0.000 description 3
- 230000036961 partial effect Effects 0.000 description 3
- 238000001514 detection method Methods 0.000 description 2
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of DC power input into DC power output
- H02M3/02—Conversion of DC power input into DC power output without intermediate conversion into AC
- H02M3/04—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters
- H02M3/10—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
- H02M3/157—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators with digital control
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Abstract
A high voltage power supply circuit comprising: the device comprises a positive high-voltage oscillating unit, a negative high-voltage oscillating unit, a voltage superposition unit, a positive high-voltage sampling unit, a negative high-voltage sampling unit, a differential amplifying unit, a high-voltage output unit, a load current sampling unit and an operational amplifying unit, wherein the input end of the positive high-voltage oscillating unit is connected with a PWM output signal, the output end of the positive high-voltage oscillating unit is connected with the first input end of the voltage superposition unit, the input end of the negative high-voltage oscillating unit is connected with the input end of a constant voltage source, the first output end of the negative high-voltage oscillating unit is connected with the second input end of the voltage superposition unit, and the output end of the voltage superposition unit outputs a high-voltage power supply. According to the application, the voltage superposition unit is arranged to superpose the voltages of the positive high-voltage oscillation unit and the negative high-voltage oscillation unit and then output a high-voltage power supply, and the high voltage output by the high-voltage output unit is fed back to the positive high-voltage oscillation unit and then the output high-voltage power supply is regulated, so that the accuracy of power supply output is improved, and the reliability is higher.
Description
Technical Field
The application relates to the field of power circuits, in particular to a high-voltage power circuit.
Background
The TX of the laser printer power supply generally needs to use a positive high voltage and a negative high voltage to superimpose and output, and needs to realize linear output by changing the output voltage along with the duty ratio of the PWM signal. In particular, at a PWM duty cycle of 0%, to output a high voltage of-1500V (30 uA on load, 50mΩ in equivalent output impedance), under which the positive high voltage converter has stopped, the TX output of the conventional high voltage power circuit is a simplified circuit obtained by dividing the voltage between the negative high voltage through shunt resistors (three 15mΩ resistors of R503, R504, R505, and a total of 45mΩ) and parallel resistors of voltage sampling resistors (two 180mΩ resistors of R515, R519, and a total of 360mΩ) and output equivalent impedance (50 mΩ), as shown in fig. 1 below.
Under the condition of a certain negative high voltage, in order to obtain enough-1500V output, bypass resistors R503, R504 and R505 are required to have very small values (45 MΩ), negative feedback voltage sampling resistors R515 and R519 have very large values (180 MΩ), and on the basis of the existing resistor production technology, the cost of the resistor with very high resistance is relatively expensive and the precision is poor, for example, the precision of the resistor with very high resistance can only reach 2% at most, and the influence of environmental temperature and humidity is very large, so that the precision of TX output voltage of a laser printer power supply is not high, and the reliability is poor; if a plurality of resistors with lower resistance values are used for series connection to replace, the cost is greatly increased due to the increase of the number of the resistors, and the difficulty in designing a circuit board is increased due to the fact that the number of the resistors is increased, and the size of a product is increased. The bypass resistance is too small, so that the power consumption is greatly increased, and the temperature rise and the service life of the product are difficult to meet the requirements of customers especially when the positive high voltage output is highest.
Disclosure of Invention
The application aims to overcome the defects in the prior art and provide a high-voltage power supply circuit with higher reliability and higher precision.
The aim of the application is realized by the following technical scheme:
a high voltage power supply circuit comprising: a positive high voltage oscillating unit, a negative high voltage oscillating unit, a voltage superposition unit, a positive high voltage sampling unit, a negative high voltage sampling unit, a differential amplifying unit, a high voltage output unit, a load current sampling unit and an operational amplifying unit,
the input end of the positive high-voltage oscillating unit is connected with a PWM output signal, the output end of the positive high-voltage oscillating unit is connected with the first input end of the voltage superposition unit, the input end of the negative high-voltage oscillating unit is connected with the input end of the constant voltage source, the first output end of the negative high-voltage oscillating unit is connected with the second input end of the voltage superposition unit, and the output end of the voltage superposition unit outputs a high-voltage power supply;
the input end of the positive high-voltage sampling unit is connected with the output end of the positive high-voltage oscillating unit, the output end of the positive high-voltage sampling unit is connected with the first input end of the differential amplifying unit, the first output end of the negative high-voltage oscillating unit is also connected with the input end of the negative high-voltage sampling unit, the output end of the negative high-voltage sampling unit is connected with the second input end of the differential amplifying unit, the output end of the differential amplifying unit is connected with the input end of the high-voltage output unit, and the output end of the high-voltage output unit is connected with the input end of the positive high-voltage oscillating unit;
the acquisition end of the load current sampling unit is connected with the second output end of the negative high-voltage oscillating unit, the output end of the load current sampling unit is connected with the current input end of the operational amplification unit, the output end of the high-voltage output unit is also connected with the voltage input end of the operational amplification unit, and the output end of the operational amplification unit realizes logic voltage output.
In an implementation manner of this embodiment, the voltage superimposing unit includes a first resistor R1 and a fifth resistor R5, a first end of the first resistor R1 is connected to the first voltage output end of the positive high voltage oscillating unit, a second end of the first resistor R1 is connected to the first end of the fifth resistor R5, and a second end of the fifth resistor R5 is connected to the first output end of the negative high voltage oscillating unit.
In an implementation manner of this embodiment, the positive high voltage sampling unit includes a third resistor R3, a first end of the third resistor R3 is connected to a connection node of the first resistor R1 and the fifth resistor R5, and a second end of the third resistor R3 is connected to the first input end of the differential amplifying unit.
In an implementation manner of this embodiment, the negative high voltage sampling unit includes a fourth resistor R4, a sixth resistor R6, and a ninth resistor R9, where a first end of the sixth resistor R6 is connected to the first voltage output end of the negative high voltage oscillating unit, a second end of the sixth resistor R6 is connected to the second input end of the differential amplifying unit after passing through the fourth resistor R4, and one end of the ninth resistor R9 is connected to the second input end of the differential amplifying unit, and the other end of the ninth resistor R6 is grounded.
In an implementation manner of this embodiment, the differential amplifying unit includes an eighth resistor R8, a third diode D3, and a differential amplifier U1A, where an anode of the third diode D3 is grounded, a cathode of the third diode D3 is connected to a first end of the eighth resistor R8 and an inverting input end of the differential amplifier U1A, a second end of the eighth resistor R8 is connected to an output end of the differential amplifier U1A, and a non-inverting input end of the differential amplifier U1A is connected to an output end of the negative high voltage sampling unit.
In an implementation manner of this embodiment, the high voltage output unit includes a zener diode D4 and a thirteenth resistor R13, a cathode of the zener diode D4 is connected to the output end of the differential amplifier U1A, an anode of the zener diode D4 is connected to the first end of the thirteenth resistor R13, a second end of the thirteenth resistor R13 is grounded, and the high voltage output unit is configured to output a positive high voltage signal through the anode of the zener diode D4.
In an implementation manner of this embodiment, the load current sampling unit includes a current collecting resistor R27, one end of the current collecting resistor R27 is connected to the second output end of the negative high voltage oscillating unit, and the other end of the current collecting resistor R27 is connected to the current input end of the operational amplifying unit.
In an implementation manner of this embodiment, the operational amplification unit includes a twenty-sixth resistor R26, a twenty-eighth resistor, and an operational amplifier U2C, where a first end of the twenty-sixth resistor R26 is connected to the output end of the high voltage output unit and the inverting input end of the operational amplifier U2C, a second end of the twenty-sixth resistor R26 is connected to the output end of the operational amplifier U2C, and a non-inverting input end of the operational amplifier U2C is connected to the output end of the load current sampling unit.
In an implementation manner of this embodiment, the high-voltage power supply circuit further includes a positive high-voltage input unit, an input end of the positive high-voltage input unit is connected with the PWM output signal, and an output end of the positive high-voltage input unit is connected with an input end of the positive high-voltage oscillating unit.
In an implementation manner of this embodiment, the high voltage power supply circuit further includes a negative high voltage input unit, an input end of the negative high voltage input unit is connected to an input end of the constant voltage source, and an output end of the negative high voltage input unit is connected to an input end of the negative high voltage oscillating unit.
Compared with the prior art, the application has at least the following advantages:
1. according to the high-voltage power supply circuit, the voltage superposition unit is arranged to superpose the voltages of the positive high-voltage oscillation unit and the negative high-voltage oscillation unit and then output a high-voltage power supply, and the high voltage output by the high-voltage output unit is fed back to the positive high-voltage oscillation unit and then is regulated to output the high-voltage power supply, so that the precision of the power supply output is improved, the application range of the power supply is wider, the precision of the high-voltage power supply circuit is high, the high-voltage power supply circuit is not easy to be interfered by high-humidity conditions, and the reliability is higher. Meanwhile, the high-voltage power supply circuit adopts the resistor with the precision of 1%, so that the precision of power supply output is further improved, and compared with the existing circuit comprising a plurality of resistors with 180MΩ, the high-voltage power supply circuit has the advantages that the cost of the product is reduced, and the reliability of the high-voltage circuit is improved.
2. The application can realize the voltage division effect by arranging the bypass resistor and realize the voltage sampling of positive high voltage output by adopting the differential amplifier, thereby avoiding the adoption of a high-value sampling resistor, improving the sampling precision, reducing the cost and reducing the loss. Meanwhile, the bypass resistor is also adopted for partial pressure sampling in negative high-voltage output, so that the negative high-voltage sampling resistor is saved, and the cost is further reduced.
Drawings
FIG. 1 is a schematic circuit diagram of a prior art high voltage power supply circuit;
FIG. 2 is a schematic block diagram of a high voltage power circuit according to an embodiment of the present application;
fig. 3 is a circuit schematic of the high voltage power supply circuit of fig. 2.
Detailed Description
In order that the application may be readily understood, a more complete description of the application will be rendered by reference to the appended drawings. The drawings illustrate preferred embodiments of the application. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
It will be understood that when an element is referred to as being "fixed to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like are used herein for illustrative purposes only and are not meant to be the only embodiment.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
In one embodiment, in order to obtain enough-1500V output under a certain negative high voltage condition, the bypass resistors R503, R504 and R505 are required to have very small values (45 mΩ), and the negative feedback voltage sampling resistors R515 and R519 have very large values (180 mΩ), while the cost of the very high resistance resistor is relatively expensive and the precision is poor based on the existing resistor production technology, such as the 180mΩ resistor, the precision can only reach 2% at most, and the influence of the environmental temperature and humidity is very large, so that the precision of the TX output voltage of the laser printer power supply is not high and the reliability is poor; if a plurality of resistors with lower resistance values are used for series connection to replace, the cost is greatly increased due to the increase of the number of the resistors, and the difficulty in designing a circuit board is increased due to the fact that the number of the resistors is increased, and the size of a product is increased. The bypass resistance is too small, so that the power consumption is greatly increased, and the temperature rise and the service life of the product are difficult to meet the requirements of customers especially when the positive high voltage output is highest. It should be noted that, because the basic function of the parallel resistor at the output end of the positive high-voltage converter is to provide a path for the negative current of the negative high-voltage converter, the positive high-voltage rectifying circuit itself cannot provide the path, and only a shunt can be provided by using the parallel resistor. This parallel resistance is a side effect of the dead or dummy load of the positive high voltage converter and is undesirable. Similarly, the parallel resistor at the negative high voltage output end provides a path or a bypass for the forward current of the positive high voltage converter. It can be understood that the values of the shunt resistors are contradictory: taking the bypass resistor at the output end of the positive high-voltage converter as an example, the bypass resistor takes a large value, which can cause overlarge negative high-voltage loss, and the bypass resistor takes a small value, which can increase the loss and heat generated by the positive high voltage on the bypass resistor and aggravate the load of the positive high-voltage converter. Therefore, the bypass resistor needs to be taken into consideration comprehensively in a compromise scheme. In the prior art, a sampling resistor is connected to the positive high-voltage output end to realize voltage sampling, and sampling current aggravates the contradiction between values of the bypass resistor, so that more loss is generated on the bypass resistor. To reduce this adverse effect, the resistance of the sampling resistor is typically very large (e.g., 360 Meg). The high-value resistor has low precision and high price, which in turn leads to reduced sampling precision and increased cost. Accordingly, the present application provides a high voltage power supply circuit comprising: the device comprises a positive high-voltage oscillating unit, a negative high-voltage oscillating unit, a voltage superposition unit, a positive high-voltage sampling unit, a negative high-voltage sampling unit, a differential amplifying unit, a high-voltage output unit, a load current sampling unit and an operational amplifying unit, wherein the input end of the positive high-voltage oscillating unit is connected with a PWM output signal, the output end of the positive high-voltage oscillating unit is connected with the first input end of the voltage superposition unit, the input end of the negative high-voltage oscillating unit is connected with the input end of a constant voltage source, the first output end of the negative high-voltage oscillating unit is connected with the second input end of the voltage superposition unit, and the output end of the voltage superposition unit outputs a high-voltage power source; the input end of the positive high-voltage sampling unit is connected with the output end of the positive high-voltage oscillating unit, the output end of the positive high-voltage sampling unit is connected with the first input end of the differential amplifying unit, the first output end of the negative high-voltage oscillating unit is also connected with the input end of the negative high-voltage sampling unit, the output end of the negative high-voltage sampling unit is connected with the second input end of the differential amplifying unit, the output end of the differential amplifying unit is connected with the input end of the high-voltage output unit, and the output end of the high-voltage output unit is connected with the input end of the positive high-voltage oscillating unit; the acquisition end of the load current sampling unit is connected with the second output end of the negative high-voltage oscillating unit, the output end of the load current sampling unit is connected with the current input end of the operational amplification unit, the output end of the high-voltage output unit is also connected with the voltage input end of the operational amplification unit, and the output end of the operational amplification unit realizes logic voltage output. According to the high-voltage power supply circuit, the voltage superposition unit is arranged to superpose the voltages of the positive high-voltage oscillation unit and the negative high-voltage oscillation unit and then output a high-voltage power supply, and the high voltage output by the high-voltage output unit is fed back to the positive high-voltage oscillation unit and then is regulated to output the high-voltage power supply, so that the precision of the power supply output is improved, the application range of the power supply is wider, the precision of the high-voltage power supply circuit is high, the high-voltage power supply circuit is not easy to be interfered by high-humidity conditions, and the reliability is higher. Meanwhile, the high-voltage power supply circuit adopts the resistor with the precision of 1%, so that the precision of power supply output is further improved, and compared with the existing circuit comprising a plurality of resistors with 180MΩ, the high-voltage power supply circuit has the advantages that the cost of the product is reduced, and the reliability of the high-voltage circuit is improved. The application can realize the voltage division effect by arranging the bypass resistor and realize the voltage sampling of positive high voltage output by adopting the differential amplifier, thereby avoiding the adoption of a high-value sampling resistor, improving the sampling precision, reducing the cost and reducing the loss. Meanwhile, the bypass resistor is also adopted for partial pressure sampling in negative high-voltage output, so that the negative high-voltage sampling resistor is saved, and the cost is further reduced. The application also provides an operational amplifying unit, namely an output current detection circuit, and a voltage signal proportional to the output current is obtained through circuit operation by the operational amplifier U2C.
For a better explanation of the above high voltage power supply circuit to better understand the concept of the above high voltage power supply circuit, please refer to fig. 2, a high voltage power supply circuit 10 includes: positive high voltage oscillating unit 100, negative high voltage oscillating unit 200, voltage superimposing unit 300, positive high voltage sampling unit 400, negative high voltage sampling unit 500, differential amplifying unit 600, high voltage output unit 700, load current sampling unit 800, and operational amplifying unit 900. The positive high voltage oscillating unit 100 is configured to output a stable positive high voltage signal, the negative high voltage oscillating unit 200 is configured to output a stable negative high voltage signal, the voltage superimposing unit 300 is configured to superimpose the voltage signals output by the positive high voltage oscillating unit 100 and the negative high voltage oscillating unit 200 and output a high voltage power supply, the positive high voltage sampling unit 400 is configured to obtain the positive high voltage signal output by the positive high voltage oscillating unit 100, the negative high voltage sampling unit 500 is configured to obtain the negative high voltage signal output by the negative high voltage oscillating unit 200, the differential amplifying unit 600 amplifies the received positive high voltage signal and the negative high voltage signal and outputs a positive high frequency voltage, the high voltage output unit 700 is configured to output a stable positive high voltage signal, the load current sampling unit 800 is configured to collect a current signal of the negative high voltage oscillating unit, and the operational amplifying unit 900 is configured to output a logic voltage signal.
Referring to fig. 2, an input end of the positive high voltage oscillating unit 100 is connected to a PWM output signal, an output end of the positive high voltage oscillating unit 100 is connected to a first input end of the voltage superposition unit 300, an input end of the negative high voltage oscillating unit 200 is connected to an input end of a constant voltage source, a first output end of the negative high voltage oscillating unit 200 is connected to a second input end of the voltage superposition unit 300, and an output end of the voltage superposition unit 300 outputs a high voltage power source; the input end of the positive high voltage sampling unit 400 is connected with the output end of the positive high voltage oscillating unit 100, the output end of the positive high voltage sampling unit 400 is connected with the first input end of the differential amplifying unit 600, the first output end of the negative high voltage oscillating unit 200 is also connected with the input end of the negative high voltage sampling unit 500, the output end of the negative high voltage sampling unit 500 is connected with the second input end of the differential amplifying unit 600, the output end of the differential amplifying unit 600 is connected with the input end of the high voltage output unit 700, and the output end of the high voltage output unit 700 is connected with the input end of the positive high voltage oscillating unit 100; the collection end of the load current sampling unit 800 is connected with the second output end of the negative high voltage oscillating unit 200, the output end of the load current sampling unit 800 is connected with the current input end of the operational amplifying unit 900, the output end of the high voltage output unit 700 is also connected with the voltage input end of the operational amplifying unit 900, and the output end of the operational amplifying unit 900 realizes logic voltage output. The PWM output signal is an externally input control voltage signal, and the constant voltage source is an externally supplied 18V constant voltage. According to the high-voltage power supply circuit, the voltage superposition unit is arranged to superpose the voltages of the positive high-voltage oscillation unit and the negative high-voltage oscillation unit and then output a high-voltage power supply, and the high voltage output by the high-voltage output unit is fed back to the positive high-voltage oscillation unit and then is regulated to output the high-voltage power supply, so that the precision of the power supply output is improved, the application range of the power supply is wider, the precision of the high-voltage power supply circuit is high, the high-voltage power supply circuit is not easy to be interfered by high-humidity conditions, and the reliability is higher.
In order to improve the application range of the power supply and improve the stability of the output voltage, the output end of the high-voltage output unit 700 is connected with the input end of the positive high-voltage oscillating unit 100, and by setting closed-loop adjustment and adopting voltage large feedback, the voltage stability is greatly improved, and by setting the positive high-frequency voltage output by feedback, the adjustment range of the output voltage can be improved, that is, the output voltage can be stabilized between-1500V and +5000V.
Referring to fig. 3, the voltage superimposing unit 300 includes a first resistor R1 and a fifth resistor R5, wherein a first end of the first resistor R1 is connected to the first voltage output end of the positive high voltage oscillating unit 100, a second end of the first resistor R1 is connected to the first end of the fifth resistor R5, and a second end of the fifth resistor R5 is connected to the first output end of the negative high voltage oscillating unit 200. The positive high-voltage sampling unit comprises a third resistor R3, a first end of the third resistor R3 is connected with a connecting node of the first resistor R1 and the fifth resistor R5, and a second end of the third resistor R3 is connected with a first input end of the differential amplifying unit. It should be noted that, in the voltage superposition unit 300, the first resistor R1 is mainly used for superposition, where the resistance value of the first resistor R1 is 43mΩ, the precision is 1%, the precision of the power output is further improved, and the resistance value used in the present application is lower, compared with the existing circuit including a plurality of resistors of 180mΩ, the cost of the product is reduced, and the reliability of the high-voltage power circuit is improved. The second end of the fifth resistor R5 is further connected to an anode output end of the positive high voltage oscillating unit 100, so, since the second end of the fifth resistor R5 is respectively connected to the output end of the positive high voltage oscillating unit 100 and the output end of the negative high voltage oscillating unit 200, one side of the fifth resistor R5 is used for collecting a negative high voltage signal and outputting a high voltage power supply after being overlapped with the first resistor R1, meanwhile, the fifth resistor R5 is also used for collecting an output signal of the positive high voltage oscillating unit 100 and inputting the output signal into the third resistor R3, and further, the third resistor R3 is used for collecting positive high voltage signals of the first resistor R1 and the fifth resistor R5 and inputting the positive high voltage signal into the differential amplifying unit.
Referring to fig. 3 again, the negative high voltage sampling unit 500 includes a fourth resistor R4, a sixth resistor R6, and a ninth resistor R9, wherein a first end of the sixth resistor R6 is connected to the first voltage output end of the negative high voltage oscillating unit, a second end of the sixth resistor R6 is connected to the second input end of the differential amplifying unit after passing through the fourth resistor R4, and one end of the ninth resistor R9 is connected to the second input end of the differential amplifying unit, and the other end is grounded. The output voltage of the negative high voltage oscillating unit may be collected by providing the fourth resistor R4, the sixth resistor R6, and the ninth resistor R9, and divided by the fourth resistor R4, the sixth resistor R6, and the ninth resistor R9, and then input into the differential amplifying unit.
In this embodiment, the differential amplifying unit 600 includes an eighth resistor R8, a third diode D3, and a differential amplifier U1A, where an anode of the third diode D3 is grounded, a cathode of the third diode D3 is connected to a first end of the eighth resistor R8 and an inverting input end of the differential amplifier U1A, a second end of the eighth resistor R8 is connected to an output end of the differential amplifier U1A, and a non-inverting input end of the differential amplifier U1A is connected to an output end of the negative high voltage sampling unit. By providing the differential amplifier U1A, interference can be filtered out, and the voltage signal can be amplified.
In this embodiment, the high voltage output unit 700 includes a zener diode D4 and a thirteenth resistor R13, where a cathode of the zener diode D4 is connected to the output end of the differential amplifier U1A, an anode of the zener diode D4 is connected to the first end of the thirteenth resistor R13, a second end of the thirteenth resistor R13 is grounded, and the high voltage output unit is configured to output a positive high voltage signal through the anode of the zener diode D4, that is, the anode of the zener diode D4 is also used as the output end of the high voltage output unit. By arranging the zener diode D4 and the thirteenth resistor R13, the stability of the output voltage can be improved, and the stability and the high efficiency of the output voltage can be ensured.
In this embodiment, the load current sampling unit 800 includes a current collecting resistor R27, one end of the current collecting resistor R27 is connected to the second output end of the negative high voltage oscillating unit, and the other end of the current collecting resistor R27 is connected to the current input end of the operational amplifying unit. The operational amplification unit 900 includes a twenty-sixth resistor R26, a twenty-eighth resistor, and an operational amplifier U2C, where a first end of the twenty-sixth resistor R26 is connected to the output end of the high-voltage output unit and the inverting input end of the operational amplifier U2C, a second end of the twenty-sixth resistor R26 is connected to the output end of the operational amplifier U2C, and a non-inverting input end of the operational amplifier U2C is connected to the output end of the load current sampling unit. By providing the current collecting resistor R27 and the operational amplifier U2C, the voltage signal (Vps) output by the high voltage output unit 700 and the current signal (ios) output by the load current sampling unit 800 can be input into the operational amplifier U2C, and the logic output voltage (service Out) can be linearly changed with the load current. In order to provide a stable acquisition voltage to the operational amplifier U2C and improve the voltage acquisition efficiency, the operational amplifier unit 900 further includes a twenty-ninth resistor R29, a twenty-fourth resistor R24, and a twenty-fifth resistor R25, one end of the twenty-ninth resistor R29 is connected to the output terminal of the high voltage output unit, the other end is connected in series with the twenty-sixth resistor R26, the first end of the twenty-fourth resistor R24 is connected to the constant voltage source, the second end of the twenty-fourth resistor R24 is connected to the connection node between the twenty-ninth resistor R29 and the twenty-sixth resistor R26, the second end of the twenty-fourth resistor R24 is further connected to the inverting input terminal of the operational amplifier U2C, the first end of the twenty-fifth resistor R25 is grounded, and the second end of the twenty-fifth resistor R25 is connected to the inverting input terminal of the operational amplifier U2C. Thus, stable acquisition voltage can be provided for the operational amplifier U2C, and the acquisition efficiency of the voltage can be improved.
It should be noted that the high voltage power supply circuit 10 further includes a positive high voltage input unit 11, an input end of the positive high voltage input unit 11 is connected to the PWM output signal, and an output end of the positive high voltage input unit 11 is connected to an input end of the positive high voltage oscillating unit 100. Further, the positive high voltage input unit 11 includes a seventeenth resistor R17, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, a twenty second resistor R22, a first capacitor C1, and a first amplifier U2A, one end of the seventeenth resistor R17 is grounded, the other end is connected to the inverting input terminal of the first amplifier U2A, one end of the twentieth resistor R20 is connected to the constant voltage source, the other end is connected to the inverting input terminal of the first amplifier U2A, a first end of the nineteenth resistor R19 is connected to the PWM output signal, a second end of the nineteenth resistor R19 is connected to the inverting input terminal of the first amplifier U2A, the non-inverting input terminal of the first amplifier U2A is connected to the output terminal of the high voltage output unit, the output terminal of the first amplifier U2A is connected to the input terminal of the positive high voltage oscillating unit after passing through the twenty second resistor R22, and a first end of the eighteenth resistor R18 is connected to the inverting input terminal of the first amplifier U2A after passing through the inverting input terminal of the first amplifier U2A. Therefore, the voltage signal of the positive high-voltage oscillating unit can be stably input, and the input PWM signal can be changed along with the output high-frequency voltage of the high-voltage output unit by setting the output high-frequency voltage of the high-voltage output unit and the non-inverting input end of the first amplifier U2A, so that the output positive high-voltage is ensured to be in a set range, namely, the output positive high-voltage is ensured to be in a range of-1500V to +5000V, the application range of a power supply is further improved, and the output precision of the high-voltage power supply is improved.
It should be noted that the high voltage power supply circuit 10 further includes a negative high voltage input unit 12, an input end of the negative high voltage input unit 12 is connected to an input end of the constant voltage source, and an output end of the negative high voltage input unit 12 is connected to an input end of the negative high voltage oscillating unit 200. Further, the negative high voltage input unit 12 includes an eleventh resistor R11, a twelfth resistor R12, a twenty-first resistor R21, a twenty-third resistor R23, a second capacitor C2, and a second amplifier U2B, where one end of the eleventh resistor R11 is connected to the constant voltage source, the other end of the eleventh resistor R11 is connected to the inverting input end of the second amplifier U2B, one end of the twelfth resistor R12 is grounded, the other end of the twelfth resistor R12 is connected to the inverting input end of the second amplifier U2B, one end of the twenty-first resistor R21 is connected to the inverting input end of the second amplifier U2B, the other end of the twenty-first resistor R21 is connected to the output end of the second amplifier U2B after passing through the second capacitor C2, and the output end of the second amplifier U2B is connected to the input end of the negative high voltage oscillating unit after passing through the twenty-third resistor R23. In this way, the negative high voltage input can be made more stable.
Compared with the prior art, the application has at least the following advantages:
according to the high-voltage power supply circuit, the voltage superposition unit is arranged to superpose the voltages of the positive high-voltage oscillation unit and the negative high-voltage oscillation unit and then output a high-voltage power supply, and the high voltage output by the high-voltage output unit is fed back to the positive high-voltage oscillation unit and then is regulated to output the high-voltage power supply, so that the precision of the power supply output is improved, the application range of the power supply is wider, the precision of the high-voltage power supply circuit is high, the high-voltage power supply circuit is not easy to be interfered by high-humidity conditions, and the reliability is higher. Meanwhile, the high-voltage power supply circuit adopts the resistor with the precision of 1%, so that the precision of power supply output is further improved, and compared with the existing circuit comprising a plurality of resistors with 180MΩ, the high-voltage power supply circuit has the advantages that the cost of the product is reduced, and the reliability of the high-voltage circuit is improved. The application can realize the voltage division effect by arranging the bypass resistor and realize the voltage sampling of positive high voltage output by adopting the differential amplifier, thereby avoiding the adoption of a high-value sampling resistor, improving the sampling precision, reducing the cost and reducing the loss. Meanwhile, the bypass resistor is also adopted for partial pressure sampling in negative high-voltage output, so that the negative high-voltage sampling resistor is saved, and the cost is further reduced. The application also provides an operational amplifying unit, namely an output current detection circuit, and a voltage signal proportional to the output current is obtained through circuit operation by the operational amplifier U2C.
Specific examples are given below to illustrate the inventive concept:
in the existing laser printer, a positive high-voltage oscillator is connected to the output end of a positive high-voltage oscillator circuit through 3 bypass resistors R503, R504 and R505 of 15MΩ, and two sampling resistors R515 and R519 of 180MΩ are connected in series to the negative feedback end of an operational amplifier. The TX high voltage output circuit in the high voltage power supply circuit of the present application needs to be able to output an adjustable voltage of-1500 VDC to +5000VDC when the PWM signal duty cycle varies from 0% to 100%. There are two limit cases: (1) As shown in fig. 1 above, when 0% duty cycle is input, R503, R504, R505 (45 mΩ) require high resistance values for achieving-1500V output load of 30uA, R515, R519 (360 mΩ). (increased accuracy and cost, increased power consumption, see description below); (2) When 100% duty cycle is input, the adjustable high voltage generator outputs the maximum positive voltage +5000VDC, then R503, R504, R505 will bear 6500VDC (5000 vdc+1500 VDC) voltage difference, power loss is great, and R503, R504, R505 also need to use multiple resistors in series to share such great voltage difference (3 resistors with 15mΩ power of 1W), so cost will rise, and space area of PCB increases.
In order to greatly reduce the design cost and improve the accuracy of power supply output, the application range of the power supply is wider, or when the positive high voltage generator outputs the maximum voltage, smaller power loss is needed, and R503, R504 and R505 are properly enlarged; to improve the accuracy of the output voltage, the resistance values of R515 and R519 should be reduced appropriately, and the above conventional circuits are limited and difficult to meet. (1) The positive high voltage and negative high voltage output are sampled and input into a differential operation circuit to directly feedback control a positive high voltage oscillator to realize the linear output required by specifications, and sampling elements (resistors) around the operation circuit are used for voltage sampling and also used for realizing the dummy load of negative voltage output, so that two 180M high-resistance sampling resistors of the original circuit can be omitted. (2) The output of the current sampling circuit and the output of the differential operation circuit are input into another operation circuit, so that the logic output of TX and load current form a certain linear proportion relation. The innovative high-voltage circuit combining the bypass resistor and the sampling resistor well solves the problems, and the circuit combines the bypass resistor at the output end of the positive high-voltage oscillator and the negative feedback sampling resistor of the operational amplifier, so that the original sampling resistor can use a resistor with a lower resistance and higher precision and can be used as the bypass resistor for realizing-1500V output.
The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.
Claims (5)
1. A high voltage power supply circuit, comprising: the device comprises a positive high-voltage oscillating unit, a negative high-voltage oscillating unit, a voltage superposition unit, a positive high-voltage sampling unit, a negative high-voltage sampling unit, a differential amplifying unit, a high-voltage output unit, a load current sampling unit and an operational amplifying unit;
the input end of the positive high-voltage oscillating unit is connected with a PWM output signal, the output end of the positive high-voltage oscillating unit is connected with the first input end of the voltage superposition unit, the input end of the negative high-voltage oscillating unit is connected with the input end of the constant voltage source, the first output end of the negative high-voltage oscillating unit is connected with the second input end of the voltage superposition unit, and the output end of the voltage superposition unit outputs a high-voltage power supply;
the input end of the positive high-voltage sampling unit is connected with the output end of the positive high-voltage oscillating unit, the output end of the positive high-voltage sampling unit is connected with the first input end of the differential amplifying unit, the first output end of the negative high-voltage oscillating unit is also connected with the input end of the negative high-voltage sampling unit, the output end of the negative high-voltage sampling unit is connected with the second input end of the differential amplifying unit, the output end of the differential amplifying unit is connected with the input end of the high-voltage output unit, the output end of the high-voltage output unit is connected with the input end of the positive high-voltage oscillating unit, the voltage superimposing unit comprises a first resistor R1 and a fifth resistor R5, the first end of the first resistor R1 is connected with the first voltage output end of the positive high-voltage oscillating unit, the second end of the first resistor R1 is connected with the first end of the fifth resistor R5, and the second end of the fifth resistor R5 is connected with the first output end of the negative high-voltage oscillating unit;
the positive high-voltage sampling unit comprises a third resistor R3, a first end of the third resistor R3 is connected with a connecting node of the first resistor R1 and the fifth resistor R5, and a second end of the third resistor R3 is connected with a first input end of the differential amplifying unit;
the negative high-voltage sampling unit comprises a fourth resistor R4, a sixth resistor R6 and a ninth resistor R9, wherein the first end of the sixth resistor R6 is connected with the first voltage output end of the negative high-voltage oscillating unit, the second end of the sixth resistor R6 is connected with the second input end of the differential amplifying unit after passing through the fourth resistor R4, and one end of the ninth resistor R9 is connected with the second input end of the differential amplifying unit;
the load current sampling unit is characterized in that an acquisition end of the load current sampling unit is connected with a second output end of the negative high-voltage oscillating unit, an output end of the load current sampling unit is connected with a current input end of the operational amplifying unit, an output end of the high-voltage output unit is also connected with a voltage input end of the operational amplifying unit, the output end of the operational amplifying unit realizes logic voltage output, the load current sampling unit comprises a current acquisition resistor R27, one end of the current acquisition resistor R27 is connected with the second output end of the negative high-voltage oscillating unit, and the other end of the current acquisition resistor R27 is connected with the current input end of the operational amplifying unit;
the differential amplifying unit comprises an eighth resistor R8, a third diode D3 and a differential amplifier U1A, wherein the anode of the third diode D3 is grounded, the cathode of the third diode D3 is respectively connected with the first end of the eighth resistor R8 and the inverting input end of the differential amplifier U1A, the second end of the eighth resistor R8 is connected with the output end of the differential amplifier U1A, and the non-inverting input end of the differential amplifier U1A is connected with the output end of the negative high voltage sampling unit.
2. The high-voltage power supply circuit according to claim 1, wherein the high-voltage output unit includes a zener diode D4 and a thirteenth resistor R13, the cathode of the zener diode D4 is connected to the output terminal of the differential amplifier U1A, the anode of the zener diode D4 is connected to the first terminal of the thirteenth resistor R13, the second terminal of the thirteenth resistor R13 is grounded, and the high-voltage output unit is configured to output a positive high-voltage signal through the anode of the zener diode D4.
3. The high-voltage power supply circuit according to claim 1, wherein the operational amplification unit comprises a twenty-sixth resistor R26, a twenty-eighth resistor and an operational amplifier U2C, a first end of the twenty-sixth resistor R26 is connected to an output end of the high-voltage output unit and an inverting input end of the operational amplifier U2C, a second end of the twenty-sixth resistor R26 is connected to an output end of the operational amplifier U2C, and a non-inverting input end of the operational amplifier U2C is connected to an output end of the load current sampling unit.
4. The high voltage power supply circuit of claim 1, further comprising a positive high voltage input unit having an input connected to the PWM output signal and an output connected to an input of the positive high voltage oscillating unit.
5. The high-voltage power supply circuit according to claim 1, further comprising a negative high-voltage input unit, an input terminal of the negative high-voltage input unit being connected to an input terminal of a constant voltage source, an output terminal of the negative high-voltage input unit being connected to an input terminal of the negative high-voltage oscillating unit.
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