CN212543649U - Frequency oscillator integrating frequency modulation mode switch power supply slow starting function - Google Patents

Frequency oscillator integrating frequency modulation mode switch power supply slow starting function Download PDF

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Publication number
CN212543649U
CN212543649U CN202021258022.5U CN202021258022U CN212543649U CN 212543649 U CN212543649 U CN 212543649U CN 202021258022 U CN202021258022 U CN 202021258022U CN 212543649 U CN212543649 U CN 212543649U
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frequency
transistor
resistor
power supply
operational amplifier
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CN202021258022.5U
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王一丁
何翔
罗润
康代涛
陈朝滨
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Chengdu Siwi Power Electronic Technology Co ltd
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Chengdu Siwi Power Electronic Technology Co ltd
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Abstract

The utility model discloses a frequency oscillator of integrated frequency modulation mode switch power supply slow start function has mainly solved current frequency oscillator and frequency bound locking circuit and has realized the problem of comparison complicacy. The slow starting circuit comprises three groups of current sources IFstart, IFmin and IFb, an oscillating capacitor CF, an operational amplifier U1, a resistor R1 and a switch K, wherein one end of the oscillating capacitor CF is connected with the other end of the three groups of current sources, the other end of the oscillating capacitor CF is grounded, the positive input end of the operational amplifier U1 is connected with the other end of the three groups of current sources, the resistor R1 and the switch K are connected with the CF in parallel after being respectively connected in series, the controlled variable reference voltage Vref is connected with the positive electrode of the operational amplifier U1 and the negative electrode of the operational. The utility model discloses reached and only realized the purpose that has the frequency oscillator circuit of frequency bound locking and frequency modulation mode switching power supply start slow start function with a small amount of components, had very high practical value and spreading value.

Description

Frequency oscillator integrating frequency modulation mode switch power supply slow starting function
Technical Field
The utility model belongs to the technical field of switching power supply's control, specifically say, relate to the frequency oscillator of integrated frequency modulation mode switching power supply slow start function.
Background
The control technology of the switching power supply is generally divided into two major categories of Pulse-Width-Modulation (PWM) and Pulse-frequency-Modulation (PFM), wherein the PWM mode adopts the mode that the switching Pulse frequency is unchanged and the Pulse duty ratio is changed to complete the regulation of the output voltage; in the PFM pulse frequency modulation mode, the working mode that the duty ratio of switching pulses is unchanged and the switching frequency is changed to complete the adjustment of output voltage is adopted. To enable the PFM mode switching power supply to work normally, only a small frequency variation range of the switching frequency is usually the normal working range of the power supply, and beyond this range, the power supply may malfunction or even be damaged. Therefore, the upper and lower limit ranges of the switching frequency need to be limited, and then the power supply determines a specific switching frequency point value in the range through an output voltage sampling feedback circuit.
The traditional analog control power supply is adopted, two frequency oscillators are used for generating a minimum frequency signal and a maximum frequency signal, then the output sampling feedback is determined, the generated switching frequency signal is compared with the two signals in each switching period, so that the switching frequency is prevented from exceeding a normal working range, the power supply needs two oscillators for generating the frequency signals, a frequency operational amplifier is needed for comparison, and resources are wasted.
By taking the most common LLC circuit of the PFM mode as an example, when the power supply is started, if the power supply adopts a closed-loop non-slow start starting mode, because the difference between the output voltage initial value and the set target voltage value is large, the sampling feedback circuit is saturated, the controller outputs the PFM pulse signal with the minimum frequency, at the moment, the LLC resonant cavity impedance is very small, the direct current gain is very large, and the filter capacitor added at the later stage is basically in a short-circuit state in the initial starting stage, so that great current impact can be caused. At the moment, a slow starting circuit is adopted for starting control, so that the circuit damage caused by overlarge starting energy is avoided. The traditional slow start technology also uses a feedback reference voltage slow start function, but in the LLC start process, although the feedback reference voltage rises very slowly, the system still starts at the lowest frequency, and still causes great impact. Therefore, how to solve the defects in the prior art is an urgent problem to be solved by the technical personnel in the field.
SUMMERY OF THE UTILITY MODEL
An object of the utility model is to provide a frequency oscillator of integrated frequency modulation mode switch power supply function of slowly starting, the frequency oscillator and frequency bound locking circuit that have mainly solved prior art existence realize more complicacy, and use the closed loop not have the start of slowly starting or feed back reference voltage start the start slowly, start energy causes the problem of impact to the power easily.
In order to realize the purpose, the utility model discloses a technical scheme as follows:
a frequency oscillator integrating a frequency modulation mode switch power supply slow start function comprises three groups of current sources IFstart, IFmin and IFb, wherein one end of the three groups of current sources IFstart, IFmin and IFb is connected with VDD after being connected in parallel, an oscillation capacitor CF, one end of the oscillation capacitor CF is connected with the other end of the three groups of current sources, a positive input end of the operational amplifier U1 is connected with the other end of the three groups of current sources, one end of the operational amplifier U1 is connected with the positive input end of the operational amplifier U1 after being connected in series, a resistor R1 and a switch K, the other end of the resistor R and the switch K are connected with the ground, the positive electrode of the controlled variable reference voltage Vref is connected with the negative input end of the operational.
Further, the current sources IFstart, IFmin include two MOS transistors Q1, Q2 whose source electrodes are simultaneously in contact with the power supply VDD, a transistor Q5 whose collector electrode is connected to the drain electrode of the MOS transistor Q1 and whose base electrode is connected to the voltage reference VrefA, a resistor Rmin whose one end is connected to the emitter electrode of the transistor Q5 and whose other end is grounded, a resistor Rstart and a capacitor Cstart whose one end is connected to the emitter electrode of the transistor Q5 and whose other end is grounded, wherein the gates of the MOS transistors Q1 and Q2 are connected to each other, the gate of the MOS transistor Q1 is connected to the drain electrode thereof to form a mirror current source, and the drain of the MOS transistor Q2 is connected to the positive input terminal of the operational amplifier.
Specifically, the current source IFb includes two MOS transistors Q3, Q4 whose sources are simultaneously in contact with the power supply VDD, a triode Q6 whose collector is connected to the drain of the MOS transistor Q3 and whose base is connected to the voltage reference VrefB, a resistor Rmax whose one end is connected to the emitter of the triode Q6, a triode output terminal of a photocoupler U2 whose collector is connected to the other end of the resistor Rmax and whose emitter is grounded, and an output sampling feedback voltage Fb whose one end is connected to the diode input terminal of the photocoupler U2 through a current limiting resistor R2 and supplies voltage to the diode input terminal, where the gates of the MOS transistors Q3 and Q4 are connected to each other, the gate of the MOS transistor Q3 is connected to the drain thereof to form a mirror current source, and the drain of the MOS transistor Q4 is connected to the positive input terminal of the operational amplifier.
Compared with the prior art, the utility model discloses following beneficial effect has:
(1) the utility model discloses a simple and easy circuit builds frequency oscillator and produces frequency signal to with feedback signal frequency generating circuit integration in the oscillator circuit, natural frequency locking mode makes switching power supply's operating frequency restriction between minimum frequency and maximum frequency, has avoided carrying out frequency operational amplifier's comparative process, and adopts and slowly start circuit to carry out start frequency control, avoids the impact that start energy caused to the power.
(2) The utility model discloses a frequency oscillator function can be accomplished to an oscillating capacitor CF, only needs a small amount of devices can carry out the bound restriction to oscillating frequency, at power start in-process, thereby carries out the control of electric current source charging current through simple and easy RC circuit and controls the set oscillation frequency, avoids causing the impact to the power.
(3) The utility model discloses a slow start circuit, the minimum frequency output is limited when starting, avoids causing the impact, and reduces minimum frequency gradually in the slow start process, finally accomplishes the start and slowly starts and gets into the closed-loop control state; the impact of the starting energy on the power supply is avoided; meanwhile, the discharge time of the oscillating capacitor CF can be adjusted by adjusting the size of the resistor R1 so as to control the size of the complementary pulse driving dead time.
Drawings
Fig. 1 is a schematic circuit diagram of the present invention.
Fig. 2 is a schematic diagram of the circuit of fig. 1 after unfolding.
Fig. 3 is a schematic diagram of a V2 voltage control driving circuit generated by the frequency oscillator of the present invention.
Fig. 4 is a waveform diagram of the frequency oscillator and driving circuit according to the present invention.
Detailed Description
The present invention will be further described with reference to the following drawings and examples, and embodiments of the present invention include, but are not limited to, the following examples.
Examples
As shown in fig. 1 to fig. 3, the frequency oscillator integrating the soft start function of the frequency modulation mode switching power supply is characterized by comprising three sets of current sources IFstart, IFmin, IFb with one ends connected to an input direct current voltage VDD in parallel, an oscillation capacitor CF with one end connected to the other ends of the three sets of current sources and the other end grounded, an operational amplifier U1 with a positive input end connected to the other ends of the three sets of current sources, a resistor R1 and a switch K connected in parallel with the CF after being connected in series, and a controlled variable reference voltage Vref with a positive electrode connected to the negative input end of the operational amplifier U1 and a negative electrode grounded, wherein the output end of the operational amplifier U1 controls the on and off of the switch K (the switch K may be a relay switch, an optical coupler switch, a MOS transistor switch, etc., without limiting the form of the switch) and the level of the controlled variable reference voltage Vref, and one end of the switch K is, the position can be reversed).
As shown in fig. 1, the circuit determines the oscillation frequency by charging and discharging the oscillation capacitor CF, i.e. the switching frequency of the power supply, the IFmin current source is a constant current source, and charges the oscillation capacitor CF at a fixed charging rate, the current source determines the minimum current for charging the oscillation capacitor CF and also determines the minimum oscillation frequency of the oscillation capacitor CF, i.e. the minimum switching frequency of the power supply; IFb the current source is a current source controlled by the power supply feedback signal to determine the specific operating frequency of the power supply; the IFstart current source works only when the power supply is started, and the minimum switching frequency threshold value is increased and slowly released to the lowest frequency through the charging current from large to small so as to achieve the purpose of slow start. The controlled variable reference Vref has two reference values of high and low, Vref is at a high reference voltage value in a circuit initial state, when the oscillation capacitor CF starts to charge and the voltage of the oscillation capacitor CF is larger than the Vref high reference voltage value, the output V2 of the operational amplifier U1 is changed from low level to high level, so that the controlled variable reference voltage Vref is controlled to be switched to the low reference voltage value, the switch K is controlled to be closed, the charge on the oscillation capacitor CF is released through the resistor R1, when the oscillation capacitor CF discharges to the Vref low reference voltage value, the output V2 of the operational amplifier U1 is changed from high level to low level, the controlled variable reference voltage Vref is controlled to be switched to the high reference voltage value, the relay switch K is opened, the oscillation capacitor CF is charged again, and the reciprocating process is completed.
As shown in fig. 2, the IFmin current source and the IFstart current source are generated by the same mirror current source, and the IFb current source is generated by another set of mirror current sources. VrefA is used as a reference voltage to generate IFmin current and IFstart current, VrefB is used as a reference voltage to generate IFb current, for example, IFmin ═ (VrefA-Vbe)/Rmin, Vbe is the BE junction voltage drop of the triode to a constant value. When the power supply is just started, because there is no charge on the capacitor Cstart, it is equivalent to that the resistors Rstart and Rmin are connected in parallel, so that the charging current is IFmin + IFstart, and the actual minimum frequency threshold is greater than the minimum frequency set in the steady state. Therefore, the power supply is prevented from being impacted due to the fact that the controller directly outputs the PFM pulse signal with the minimum frequency in the starting process. IFb the current sources are generated by another set of current sources, Fb is the output sampling feedback voltage of the power supply, and can be isolated by an optical coupler U2. The feedback voltage signal of the switching power supply controls the conduction degree of the triode output electrode of the optocoupler U2 to determine the size of the IFb current source, so that the specific working frequency of the power supply is determined, when the triode output electrode of the U2 is completely conducted, the IFb maximum current is limited by the Rmax resistor, the current of the IFb current source is (IFb max ═ VrefB-Vbe)/Rmax), the maximum charging current of the oscillation capacitor CF is IFmin + IFbmax, and the oscillation working frequency of the CF voltage at the moment is the maximum limit frequency Fmax. When the output negative feedback voltage Fb changes, IFb current also changes, the charging frequency of the oscillation capacitor CF changes, so that the working frequency of the power supply also changes along with the change, but the working frequency does not exceed the upper and lower frequency limit threshold, and a closed loop system is formed.
As shown in fig. 3, the U2D flip-flop, the U3 inverter, the U4 and gate, and the U5 and gate constitute a driving circuit. The voltage V2 generated by the operational amplifier output in the frequency oscillator is a pulse driving dead zone voltage and is connected to the input end of the driving circuit, V3 and V4 are complementary driving outputs, and the pulse width of the voltage V2 is the dead zone time and is controlled by the R1 discharge resistor. Switching is performed at the high and low threshold points of the VCF voltage, and the dead time between the two sets of complementary drive voltages is adjusted by the discharge time of resistor R1.
As shown in fig. 4, in which the abscissa represents the time axis and the ordinate represents the output voltage. VCF in the simulation waveform is the voltage on the oscillation capacitor CF and is in a back-and-forth oscillation state, V3 and V4 are complementary driving waveforms, are controlled by the VCF voltage to be alternately output, and are converted at a high level threshold point and a low level threshold point of the VCF voltage; the magnitude of the dead time between the two sets of complementary driving voltages is controlled by the voltage of V2, and can be adjusted by the discharge time of the resistor R1.
The utility model discloses a frequency oscillator function can be accomplished to an oscillating capacitor CF and a small amount of components and parts to carry out the upper and lower limit restriction to oscillation frequency, at power start in-process, thereby carry out the control of electric current source charging current through simple and easy RC circuit and control opening machine oscillation frequency, avoid causing the impact to the power.
The above-mentioned embodiment is only the preferred embodiment of the present invention, and is not a limitation to the protection scope of the present invention, but all the changes made by adopting the design principle of the present invention and performing non-creative work on this basis should belong to the protection scope of the present invention.

Claims (3)

1. The frequency oscillator is characterized by comprising three groups of current sources IFstart, IFmin and IFb, one ends of the three groups of current sources IFstart, IFmin and IFb are connected with an input direct-current voltage VDD in parallel, an oscillating capacitor CF, one end of the oscillating capacitor CF is connected with the other ends of the three groups of current sources, the positive input end of the operational amplifier U1 is connected with the other ends of the three groups of current sources, a resistor R1 and a switch K which are connected with the CF in parallel after being respectively connected in series, and a controlled variable reference voltage Vref, the positive pole of the controlled variable reference voltage Vref is connected with the negative input end of the operational amplifier U1, and the negative pole of the controlled variable reference voltage Vref is grounded, wherein the level V2 of the.
2. The frequency oscillator of claim 1, wherein the current sources IFstart, IFmin comprise two MOS transistors Q1, Q2 having sources connected to the input dc power VDD, a transistor Q5 having a collector connected to the drain of the MOS transistor Q1 and a base connected to the voltage reference VrefA, a resistor Rmin having one end connected to the emitter of the transistor Q5 and the other end connected to ground, and a resistor Rstart and a capacitor Cstart having one end connected to the emitter of the transistor Q5 and the other end connected to ground after being connected in series, wherein the gates of the MOS transistors Q1 and Q2 are connected to each other, the gate of the transistor Q1 is connected to the drain thereof to form a mirror current source, and the drain of the transistor Q2 is connected to the positive input terminal of the operational amplifier.
3. The frequency oscillator of claim 2, wherein the current source IFb comprises two MOS transistors Q3 and Q4 having their sources in contact with the power supply VDD, a transistor Q6 having its collector connected to the drain of the MOS transistor Q3 and its base connected to the voltage reference VrefB, a resistor Rmax having one end connected to the emitter of the transistor Q6, a transistor output of a photocoupler U2 having its collector connected to the other end of the resistor Rmax and its emitter grounded, and an output sampled feedback voltage Fb having one end connected to the diode input of the photocoupler U2 through a current limiting resistor R2 and providing a voltage to the diode input, wherein the gates of the MOS transistors Q3 and Q4 are connected to each other, the gate of the MOS transistor Q3 is connected to its drain to form a mirror current source, and the drain of the MOS transistor Q4 is connected to the positive input of the operational amplifier.
CN202021258022.5U 2020-06-30 2020-06-30 Frequency oscillator integrating frequency modulation mode switch power supply slow starting function Active CN212543649U (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111934529A (en) * 2020-06-30 2020-11-13 成都四威功率电子科技有限公司 Frequency oscillator integrating frequency modulation mode switch power supply slow starting function
WO2023087835A1 (en) * 2021-11-16 2023-05-25 北京卫星制造厂有限公司 Spaceborne secondary power supply single event transient suppression circuit

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111934529A (en) * 2020-06-30 2020-11-13 成都四威功率电子科技有限公司 Frequency oscillator integrating frequency modulation mode switch power supply slow starting function
WO2023087835A1 (en) * 2021-11-16 2023-05-25 北京卫星制造厂有限公司 Spaceborne secondary power supply single event transient suppression circuit

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