CN203193474U - Voltage-controlled oscillator - Google Patents
Voltage-controlled oscillator Download PDFInfo
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- CN203193474U CN203193474U CN 201320120854 CN201320120854U CN203193474U CN 203193474 U CN203193474 U CN 203193474U CN 201320120854 CN201320120854 CN 201320120854 CN 201320120854 U CN201320120854 U CN 201320120854U CN 203193474 U CN203193474 U CN 203193474U
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- voltage
- timing
- controlled oscillator
- frequency
- timing capacitor
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Abstract
The utility model relates to a voltage-controlled oscillator comprising a timing resistor, a timing capacitor, a voltage regulating tube and a feedback optical coupler, wherein one end of the timing resistor is connected with the timing capacitor, the other end of the timing resistor is connected with a cathode end of the voltage regulating tube, the other end of the timing capacitor is connected with one end of the feedback optical coupler, and the other end of the feedback optical coupler is connected with an anode end of the voltage regulating tube. With the voltage-controlled oscillator, the conduction time and frequency of a flyback converter of a fixed frequency-current mode can be changed, and a switching power supply of a system can work steadily and normally under the condition that high voltage is input.
Description
Technical field
The utility model relates to electric and electronic technical field, particularly the voltage controlled oscillator in a kind of photovoltaic generation switch power supply system.
Background technology
Traditional off-line type anti exciting converter is to utilize special-purpose pwm chip hardware to control, and the most frequently used have UC3844, UC3824, a TL494 etc.The switching frequency of these pwm chip control switch power drives pulses is fixed.Wherein the off-line type Switching Power Supply control chip of maximum outputs of usefulness mostly is UC3844, its theory diagram is as shown in Figure 1: wherein control circuit is controlled by UC3844, configure that the switching frequency of system drive just can not change after the frequency of oscillation, no matter be input voltage high situation or the low shape of input voltage.Under the continuous state, the utilance of main switch element and transformer all can improve.Electric current all can take place intermittently at primary winding and secondary coil, and the ripple current of output capacitor is big.Because the control characteristics of continuous type and discontinuous type are different, so manage to make system stability just to seem very important.Owing to the difference of input voltage, make the linear change rate difference of transformer inductance electric current, so the ON time of power switch pipe is also different fully; The ON time of power MOSFET tube is very short when high pressure is imported, and only is 300-600ns, and the instantaneous peak current that power MOSFET tube flows through is very big; Saturation condition may take place when power MOSFET tube is closed.The result can not open power transfer linearly when conducting, cause the decrease in efficiency of converter and reliability to reduce.
When above-mentioned shortcoming causes the input voltage when Switching Power Supply very high, the driving pulse of output will become very narrow, simultaneously in order to take into account the dimensional requirement of transformer, have only the switching frequency of raising can satisfy the high requirement of input voltage, it is too high that but switching frequency can not be carried, because too high switching frequency causes the loss of Switching Power Supply to become big, thereby make the efficient of system reduce, this loses more than gain in the photovoltaic system Switching Power Supply, because the Switching Power Supply of this type systematic all requires loss little, thereby improve the overall efficiency of inverter, this is particularly important in the single-phase photovoltaic combining inverter of small-power.
In order to solve the needs of high input voltage, can change control chip, but need in the design of system from new change, workload and experimental amount are all bigger, relatively more commonly used is to change Current Control cake core NCP1351, and this model control chip has frequency conversion function, but design need be done bigger change, this expense and time concerning the user that system schema has all been finalized the design are all longer, comparatively uneconomical.
In sum, need seek at present a kind ofly do not changing the simplest method of original big control framework and control chip.
Summary of the invention
The utility model provides a kind of voltage controlled oscillator, and the utility model can make ON time and the frequency of the inverse excitation type converter of fixed frequency-current-mode be changed, reach the input high pressure situation under the system switching power supply can stablize operate as normal.
The technical scheme that realizes above-mentioned purpose is as follows:
A kind of voltage controlled oscillator, comprise timing resistor, timing capacitor, voltage-stabiliser tube and feedback optocoupler, one end of described timing resistor is connected with timing capacitor, the other end of timing resistor is connected with the cathode terminal of voltage-stabiliser tube, the other end of timing capacitor is connected with an end of feedback optocoupler, and the other end of feedback optocoupler is connected with the anode tap of voltage-stabiliser tube.
Further, described timing capacitor is the timing capacitor of 220pF, and timing resistor is the timing resistor of 27K Ω.
The beneficial effects of the utility model are, adopt frequency conversion of the present utility model to change the mode of duty ratio, can be under the condition that does not influence existing main circuit and most of control circuit, and reach under the situation of input high pressure the system switching power supply and can stablize operate as normal.Improved the efficient of system simultaneously, in the wide application prospect of having of photovoltaic combining inverter.This reality is novel if use direct voltage as control voltage in addition, and voltage controlled oscillator can be made into frequency adjustment signal source very easily.
Below in conjunction with the drawings and specific embodiments the utility model is described in further detail.
Description of drawings
Fig. 1 is the flyback power supply block diagram (because switching frequency is fixed, can only satisfy the not high occasion of input voltage) of traditional UC3844 chip controls;
Fig. 2 is the inverse-excitation type switch power-supply block diagram that voltage controlled oscillator of the present utility model connects the UC3844 chip controls;
Fig. 3 is voltage-controlled oscillator circuit principle schematic of the present utility model;
Fig. 4 is voltage controlled oscillator operation principle schematic diagram;
Embodiment
With reference to Fig. 2 and Fig. 3, voltage controlled oscillator of the present utility model comprises timing resistor R1, timing capacitor C1, voltage-stabiliser tube Z1 and feedback optocoupler U1.The end of timing resistor R1 is connected with timing capacitor C1, and the other end of timing resistor R1 is connected with the cathode terminal of voltage-stabiliser tube Z1, and the other end of timing capacitor C1 is connected with the end of feedback optocoupler U1, and the other end of feedback optocoupler U1 is connected with the anode tap of voltage-stabiliser tube.Described timing capacitor is the timing capacitor of 220pF, and timing resistor is the timing resistor of 27K Ω.
The error amplifier that 3.3V voltage-stabiliser tube Z1 is connected the UC3844 chip was accepted the variation of whole output voltage afterwards.When input voltage minimum, and power output full load, the duty ratio of power switch pipe will be above 50%, the input voltage of voltage controlled oscillator will reach 7.7V.Timing capacitor C1 and timing resistor R1 have determined maximum operation frequency, are 220pF such as the value of timing capacitor in the utility model, and the timing resistor resistance is 27K Ω, and frequency of oscillation is 140KHz.When the input voltage of voltage controlled oscillator greater than 3.3V, the voltage controlled oscillator starting oscillation, voltage controlled oscillator can produce the zigzag waveform, its frequency is determined by the resistance that links to each other with error amplifier and electric capacity.Voltage controlled oscillator begins starting of oscillation by the highest frequency FMAX140KHz, and frequency descends gradually afterwards, until minimum frequency FMIN75KHz.
Shown in Figure 4 is the voltage controlled oscillator operation principle, and voltage-controlled element generally all is to use variable capacitance diode, and its capacitance is subjected to the control of input voltage Vc (t); V
cDuring variation, namely cause frequency of oscillation f
0Change.Therefore, voltage controlled oscillator in fact is exactly a kind of frequency to voltage converter, and its characteristic can be used the ringing frequency f
vAnd the relation curve between the control voltage Vc is represented.Centre frequency f on Fig. 4
0Be not add the natural mode shape of control during voltage within the specific limits, f
vWith V
cBetween be linear relationship.In the range of linearity, this linearity curve can be used following The Representation Equation: f
v(t)=f
0+ K
vVc (t); In the formula, K
vBe characteristic slope, be called gain or the sensitivity of VCO; The size that the caused angular frequency of its representation unit control voltage changes.
Claims (2)
1. voltage controlled oscillator, it is characterized in that: comprise timing resistor, timing capacitor, voltage-stabiliser tube and feedback optocoupler, one end of described timing resistor is connected with timing capacitor, the other end of timing resistor is connected with the cathode terminal of voltage-stabiliser tube, the other end of timing capacitor is connected with an end of feedback optocoupler, and the other end of feedback optocoupler is connected with the anode tap of voltage-stabiliser tube.
2. voltage controlled oscillator according to claim 1, it is characterized in that: described timing capacitor is the timing capacitor of 220pF, timing resistor is the timing resistor of 27K Ω.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201320120854 CN203193474U (en) | 2013-03-17 | 2013-03-17 | Voltage-controlled oscillator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201320120854 CN203193474U (en) | 2013-03-17 | 2013-03-17 | Voltage-controlled oscillator |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN203193474U true CN203193474U (en) | 2013-09-11 |
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ID=49110302
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 201320120854 Expired - Fee Related CN203193474U (en) | 2013-03-17 | 2013-03-17 | Voltage-controlled oscillator |
Country Status (1)
| Country | Link |
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| CN (1) | CN203193474U (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110868778A (en) * | 2019-11-18 | 2020-03-06 | 深圳智芯半导体科技有限公司 | Constant current control method for low-voltage difference of LED driving input and output |
-
2013
- 2013-03-17 CN CN 201320120854 patent/CN203193474U/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110868778A (en) * | 2019-11-18 | 2020-03-06 | 深圳智芯半导体科技有限公司 | Constant current control method for low-voltage difference of LED driving input and output |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20130911 Termination date: 20180317 |