Control method of ultra-wide-voltage high-voltage input power supply

Abstract

The invention discloses an ultra-wide-voltage high-voltage power supply control method, and the method comprises the steps: a wide-voltage starting circuit which is used for low-voltage and low-power-consumption rapid starting and has a voltage sampling output function; the frequency adjusting function is used for low-voltage quick start; bootstrap power supply of the capacitor is realized, so that secondary start (hiccup) is avoided; and volt-second integral control is used for saturation control of the isolation transformer. And the PWM controller is used for power control of the signal generator. And the wide-voltage starting circuit realizes low-voltage quick starting, outputs a signal for external control, meets the requirement of extremely wide voltage, and must be electrified again to start after the system is shut down due to a fault. And the requirement of low power consumption is met under extremely high voltage. And a frequency adjusting function: high-power quick starting can be realized at the starting moment. Capacitor bootstrap power supply is an effective solution for avoiding secondary starting. Volt-second integral control: the transformer is efficiently utilized, and the size of the transformer is greatly reduced. And the PWM controller is used for realizing all effective control functions on the power.

Description

Technical Field

[0001] The present invention relates to the field of power electronic technology, and in particular to the field of ultra-wide voltage and high voltage power conversion. Background Art

[0002] With the rapid development of semiconductor technology, the field of power electronics has penetrated into the field of high-power closed loop. In the field of high-voltage power supply input, especially ultra-high voltage power supply, low-power power supply of about 100W has a good application.

[0003] In the past, ultra-wide voltage power supplies had very low power, and ultra-wide voltage power supply units of around 100W have always been difficult to design because of their low starting voltage (theoretically, the lower the better), extremely high voltage shock (3000V or 4500V), small size, and high isolation (8000Vac).

[0004] Wide voltage power supplies on the market still use conventional control methods, but due to low power, low voltage, no requirements for startup speed, low safety requirements, redundant design, large device margin, it is easy to meet the design requirements. From the perspective of startup speed and safety, they do not meet the requirements of high reliability. Summary of the invention

[0005] The problem to be solved by the present invention is to provide a safety control method for an ultra-wide voltage high-voltage power supply to overcome the problems of short low-voltage startup time, insufficient withstand voltage, large static power, insufficient power, multiple startups, and safety protection in the prior art.

[0006] In order to achieve the above object, the technical solution of the present invention provides a safety control method for an ultra-wide voltage and high voltage power supply, and the control method includes:

[0007] Wide voltage starting circuit, used for fast and safe starting of ultra-wide voltage and high voltage converters;

[0008] The power supply is bootstrapped to avoid hiccup start or secondary start.

[0009] Low-voltage frequency adjustment circuit can meet the low-voltage quick start requirements to the greatest extent;

[0010] The volt-second integral control circuit makes reasonable use of the isolation transformer (or inductor) to reduce the volume and stabilize the control;

[0011] Preferably, the wide voltage starting circuit has a starting voltage judgment function and starts within a certain voltage range.

[0012] Preferably, the wide voltage starting circuit has a single pulse output function, and the pulse width meets the minimum starting time requirement.

[0013] Preferably, the wide voltage startup circuit has high voltage resistance, and the sampling voltage utilizes capacitors to balance resistance, and has low power consumption standby capability.

[0014] Preferably, the bootstrap power supply circuit solves the problem of insufficient auxiliary energy by connecting a large capacitor in parallel with the rectifier diode.

[0015] Preferably, the frequency adjustment circuit changes the operating frequency within an appropriate low voltage range.

[0016] Preferably, the volt-second integration control circuit achieves the purpose of safety control by adjusting the limit of the output pulse width when working at high voltage.

[0017] Compared with the prior art, the technical solution of the present invention has the following characteristics:

[0018] It only starts at low voltage to meet the power-on process conditions. There is no startup process at normal high voltage, and in high-voltage applications, it will not cause fault expansion.

[0019] Quick start, fast start process. Due to the enhanced low-voltage start process, during the start process, there is no secondary power-on phenomenon and the voltage always rises monotonically.

[0020] It has volt-second integral control to maximize the use of magnetic device capabilities and ensure that the magnetic devices always work within a reasonable range, adding another layer of safety protection to the power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of power conversion in the prior art;

[0022] Figure 2 An improved method for repowering circuits;

[0023] Figure 3 This is a schematic diagram of a commonly used startup circuit for a low voltage DC converter;

[0024] Figure 4 It is a schematic diagram of a low-power pulse starting circuit of the present invention;

[0025] Figure 5 A schematic diagram of a variable frequency starting circuit of the present invention;

[0026] Figure 6 The inductor current waveform of the variable frequency starting of the present invention;

[0027] Figure 7 The bootstrap power supply principle diagram of the present invention;

[0028] Figure 8 Schematic diagram of bootstrap power supply with voltage regulator and adjustment tube;

[0029] Fig. 9A schematic diagram of a volt-second integral limiting circuit; DETAILED DESCRIPTION

[0030] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0031] Figure 1 This is a commonly used control method for isolated power converters in the market. Among them, R1, C1, and VD1 constitute the startup control of the auxiliary power supply. When the input power is powered on, R1 charges C1. After reaching the device turn-on threshold voltage, it outputs PWM pulses to control the operation of the subsequent switch tube and re-supply power through the transformer VD1. Before the transformer re-powers, the energy stored in C1 is used to power the control chip.

[0032] The startup time of the power supply depends on the charging time of R1 and C1, as well as the energy stored in C1. In order to achieve the purpose of fast startup, R1 and C1 cannot be too large. Therefore, fast startup is a difficult point in high-voltage applications. R1 cannot be too small, otherwise the power consumption will be too large. To solve this problem, high-voltage power supply will adopt Figure 2 This method only improves the stability of the auxiliary power supply. Since C1 can be appropriately reduced, the stability at the start-up moment is improved and the frequency of secondary starting is reduced.

[0033] Figure 3 This is a common power supply method for low-voltage starting power supply. Due to the use of auxiliary NPN tubes VT1 and VZ1, the auxiliary power supply is always stable during the starting process, without secondary starting phenomenon, and the normal auxiliary power supply voltage is slightly greater than the starting voltage setting value. This power supply method still cannot solve the high-voltage starting problem. At the same time, the power is too large at the moment of starting, and VT1 is easy to burn out. It should be improved in the actual system.

[0034] With reference to the previous starting circuit, the starting power supply circuit was redesigned and improved, such as Figure 4 .

[0035] Through R3 and VT2, the current flowing through VZ1 is close to constant current, which stabilizes VZ1. At the same time, the collector current of VT2 is proportional to the power supply voltage (the error can be ignored). The power-on signal and input voltage sampling model are obtained through the subsequent "voltage sampling and power-on output".

[0036] The power-on signal passes through the subsequent "monostable generator" to send out a pulse signal with the longest startup time, and through the VT3 switch, a high current output signal is given to the subsequent stage to quickly start the converter. The purpose of this pulse impact is to supply power to the auxiliary power supply and start the control chip in time.

[0037] Among them, C3 and C4 are capacitors connected in series to achieve ultra-high voltage and reduce the capacitor withstand voltage level. R1, R3, R4, and VZ4 form a static discharge circuit of the capacitor to balance the capacitor voltage. VT1 and VT4 achieve ultra-high withstand voltage series application and reduce the transistor withstand voltage.

[0038] Through this startup circuit, the power consumption of the startup control circuit is reduced to the maximum extent.

[0039] Figure 5 Frequency adjustment circuit. Frequency adjustment is different from the frequency modulation working mode. This circuit is equivalent to CCCS, which changes the charging time and adjusts the working frequency by adjusting the charging current. When the voltage reaches the normal working value, this function fails. The role of frequency adjustment is: by controlling the inductor ripple, it can output more power than the normal peak current control at startup, which is conducive to quick startup.

[0040] Figure 6 , variable frequency starting inductor current waveform. In the peak control mode, under the same inductor current change rate and duty cycle (startup) conditions, the higher the frequency, the higher the average current.

[0041] Figure 7 , bootstrap power supply mode. Since more energy is required in high-voltage isolation drive, the power supply voltage drops quickly when conventional power supply mode is used, and the power supply secondary startup phenomenon caused by insufficient power supply will occur. This phenomenon is not conducive to the safety of the power supply. The present invention solves this problem by combining diodes and capacitors and adopting a bootstrap power supply mode. There is no similar solution in the public power supply scheme. The method is to Figure 2 C2 of the circuit is connected in parallel to both ends of the VD1 diode.

[0042] Figure 7 , C2 is charged through R1 during startup. During the startup process, as the output voltage increases, the voltage obtained by the auxiliary transformer through the rectification of VD2 gradually increases, and the energy is also synchronously provided to the auxiliary power supply through the capacitor, synchronously offsetting the energy loss of the auxiliary power supply. The secondary startup phenomenon is completely avoided. Since the starting pulse is only used to start the auxiliary power supply capacitor, the energy supply is mainly provided by the bootstrap capacitor. From the perspective of safe use, there are the following advantages: in any abnormal load situation, since the energy cannot be supplied normally through the bootstrap capacitor, the chip will quickly enter the undervoltage lockout state (the control chip has an undervoltage shutdown function) due to insufficient power supply, protecting the system and avoiding secondary failures of the power supply system.

[0043] Figure 8 , a schematic diagram of a bootstrap power supply with a voltage regulator and a regulator. During startup, C2 is charged through R2, with the voltage on the left positive and the voltage on the right negative. During normal startup, the voltage on R2 increases with the load voltage, and C2 is connected in series with the voltage on R2 to supplement the control circuit with power. This structure avoids Figure 2 During the startup process, the output voltage builds up slowly and the control circuit drops due to insufficient energy.

[0044] Fig. 9 , a schematic diagram of a volt-second integral limiting circuit. For a transformer or inductor with a given number of turns, a given core cross-sectional area, and a given material, in order to avoid saturation of the magnetic material, the transformer or inductor works well in the designed linear region. The volt-second integral limiting function can achieve a stable control function. Compared with only using peak current control, the use of volt-second integral limiting in large transformers can better make the magnetic material work within a reasonable range. Avoid inductance changes caused by sudden load changes that exceed the controlled range. Under the requirements of ultra-high input voltage, low operating frequency, and pursuit of small volume magnetic materials. The transformer or inductor may be saturated within a working cycle.

[0045] Fig. 9 In the circuit, the differential constants of C6 and R9 determine the maximum pulse width, and under the condition of fixed frequency, the maximum duty cycle. Under the volt-second integral control (R10, R11, R12, VT6) function, the pulse width is further controlled by sampling the input voltage VINSENS, which becomes narrower as the input voltage increases, thereby limiting the volt-second integral V×t of the transformer or inductor.

[0046] Through the above design inventions and control improvements, the 120W output requirement can be achieved within an extremely wide input voltage range of 100V to 3000V, and has been applied in national key projects.

[0047] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A control method for an ultra-wide voltage and high voltage input power supply, characterized in that: The controller comprises: Wide voltage startup circuit, used for ultra-wide voltage and ultra-low power consumption startup control; Power supply bootstrap circuit to avoid hiccup start or secondary start; Frequency adjustment circuit can meet the low voltage quick start requirements to the greatest extent; The volt-second integral control circuit makes reasonable use of the isolation transformer (or inductor) to reduce the volume and stabilize the control.

2. The wide voltage starting circuit according to claim 1, characterized in that: The starting unit comprises: an undervoltage fixed-width pulse starting signal and an extremely low power consumption control circuit.

3. The wide voltage starting circuit according to claim 1, characterized in that: The startup unit includes: taking power through a balancing resistor connected in series with a capacitor, and a switch tube structure connected in series.

4. The power bootstrap power supply circuit according to claim 1, characterized in that: The auxiliary supply is powered by a bootstrap supply across the supply diode.

5. The frequency adjustment circuit according to claim 1, characterized in that Frequency conversion control is only used within a certain low voltage range.

6. The volt-second integration control circuit according to claim 1, characterized in that At the same time, the driving voltage and input voltage are sampled to control the charging and discharging process of the capacitor and achieve the purpose of volt-second integral control.

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