Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a high-efficiency milliwatt photovoltaic energy collection control circuit.
In order to achieve the purpose of the invention, the invention adopts the technical scheme that:
a high-efficiency milliwatt photovoltaic energy collection control circuit is characterized by comprising an energy storage circuit, a controlled switch circuit and a double-voltage control circuit, wherein,
the controlled switch circuit comprises a MOS field effect transistor M1 and a bias circuit, and the bias circuit is connected to the MOS field effect transistor M1;
the double-voltage control circuit comprises a conducting voltage control circuit and a closing voltage control circuit;
the input end of the breakover voltage control circuit is connected with the output end of the energy storage circuit, and the output end of the breakover voltage control circuit is connected with the biasing circuit;
the input end of the turn-off voltage control circuit is connected with the drain electrode of the MOS field effect transistor M1, and the output end of the turn-off voltage control circuit is connected with the bias circuit.
The beneficial effect of above-mentioned scheme is that, when being applied in the room to thing networking sensing node, when the power supply is difficult, if adopt energy harvesting can only obtain milliwatt level photovoltaic energy supply usually, the electric energy of collection is difficult to high-efficiently match traditional DC-DC conversion circuit.
According to the invention, the high-efficiency control circuit is designed between the photovoltaic cell and the DC-DC conversion circuit, so that the high-efficiency collection of milliwatt-level photovoltaic energy is realized, and the low-power-consumption node can be normally driven to normally work or the cell can be charged for energy storage. Therefore, the deployment difficulty caused by the power supply difficulty of the nodes of the Internet of things in the application scene is reduced, the implementation difficulty and cost of replacing the primary battery in the traditional mode are reduced, and the technical support is provided for realizing the application deployment scheme of the Internet of things which is environment-friendly.
The static power consumption of the designed circuit is very low, the working voltage range is wide, and the hardware cost is very low, thereby being beneficial to popularization and application of results.
Further, the energy storage circuit comprises an energy storage capacitor C1 and an external photovoltaic cell, wherein the energy storage capacitor C1 is connected with the external photovoltaic cell in parallel, and the anode of the energy storage capacitor C1 is connected with the anode of the external photovoltaic cell and the cathode of the energy storage capacitor C1 is connected with the ground.
Further, the MOS field effect transistor M1 is a P-channel enhancement type MOS field effect transistor, wherein the source of the MOS field effect transistor M1 is connected to the anode of the energy storage capacitor C1; the drain electrode of the MOS field effect transistor M1 is the output end of the high-efficiency milliwatt photovoltaic energy collection control circuit; the gate of the MOS field effect transistor M1 is connected with a bias circuit.
Further, the bias circuit comprises a resistor R1 and a resistor R5, wherein one end of the resistor R1 is connected with the anode of the energy storage capacitor C1, the other end of the resistor R1 is connected with the resistor R5 in series, and the connection point of the resistor R1 and the resistor R5 is connected with the gate of the MOS field effect transistor M1.
The beneficial effect of the above further scheme is that M1 can be respectively operated in the saturation conducting state and the cut-off state under the control of the bias voltage. When M1 is in saturation conduction, the energy storage circuit provides electric energy for the DC-DC conversion circuit, and the DC-DC conversion circuit works normally; when M1 is up, the energy storage circuit stops providing power for the DC-DC conversion circuit, and the DC-DC conversion circuit stops working.
Further, the on-state voltage control circuit comprises a darlington composite tube formed by a triode T1 and a triode T2, a voltage division circuit formed by serially connecting a resistor R2 and a sliding resistor R3, and a resistor R4, wherein one end of the voltage division circuit formed by serially connecting a resistor R2 and a sliding resistor R3 is connected with the anode of the energy storage capacitor C1, and the other end of the voltage division circuit is grounded; the moving contact of the sliding resistor R3 is connected with the base electrode of the triode T1 through the resistor R4 and provides static operating point bias voltage for the triode T1 and the triode T2; the emitter of the triode T2 is connected with the ground; the collector of the triode T1 and the collector of the triode T2 are connected in parallel with the negative electrode of the diode D1; the anode of the diode D1 is connected with the resistor R5.
The further scheme has the advantages that when the voltages at the two ends of the energy storage circuit are higher than the set voltage Von, the conduction voltage control circuit drives the controlled switch circuit to be in a conduction state, the energy storage circuit provides electric energy for the DC-DC conversion circuit, the DC-DC conversion circuit works normally, and the selected voltage Von can guarantee that high energy conversion efficiency of the photovoltaic cell is obtained.
Furthermore, the turn-off voltage control circuit comprises a Darlington composite tube formed by a triode T3 and a T4, a voltage division circuit formed by serially connecting a resistor R7 and a sliding resistor R8, and a resistor R6, wherein one end of the voltage division circuit formed by serially connecting a resistor R7 and a sliding resistor R8 is connected with the drain electrode of the MOS field effect tube M1, and the other end of the voltage division circuit is grounded; the moving contact of the sliding resistor R8 is connected with the base electrode of the triode T3 through the resistor R6 and provides static operating point bias voltage for the triode T3 and the triode T4; the emitter of the triode T4 is grounded; the collector of the transistor T3 and the collector of the transistor T4 are connected in parallel with the cathode of the diode D2, and the anode of the diode D2 is connected with the resistor R5.
The further scheme has the advantages that when the voltages at the two ends of the energy storage circuit are higher than the set voltage Voff, the voltage control circuit is turned off to drive the controlled switch circuit to be in a conducting state, the energy storage circuit provides electric energy for the DC-DC conversion circuit, the DC-DC conversion circuit works normally, and although the selected voltage Voff is smaller than Von, the high energy conversion efficiency of the photovoltaic cell can be guaranteed.
When the voltage of the two ends of the energy storage circuit is lower than the set voltage Von, the voltage control circuit is conducted to stop driving; and when the voltage at the two ends of the energy storage circuit is lower than the set voltage Voff, the voltage control circuit is closed to stop driving. When the on-voltage control circuit and the off-voltage control circuit are both stopped to be driven, M1 is cut off, and the energy storage circuit stops supplying electric energy to the DC-DC conversion circuit.
Detailed Description
The following description of the embodiments of the present invention is provided to facilitate the understanding of the present invention by those skilled in the art, but it should be understood that the present invention is not limited to the scope of the embodiments, and it will be apparent to those skilled in the art that various changes may be made without departing from the spirit and scope of the invention as defined and defined in the appended claims, and all matters produced by the invention using the inventive concept are protected.
A high-efficiency milliwatt photovoltaic energy collection control circuit is shown in figure 2, and comprises an energy storage circuit, a controlled switch circuit and a dual-voltage control circuit, wherein,
the controlled switch circuit comprises a MOS field effect transistor M1 and a bias circuit, and the bias circuit is connected to the MOS field effect transistor M1;
the double-voltage control circuit comprises a conducting voltage control circuit and a closing voltage control circuit;
the input end of the breakover voltage control circuit is connected with the output end of the energy storage circuit, and the output end of the breakover voltage control circuit is connected with the biasing circuit;
the input end of the turn-off voltage control circuit is connected with the drain electrode of the MOS field effect transistor M1, and the output end of the turn-off voltage control circuit is connected with the bias circuit.
Specifically, the energy storage circuit comprises an energy storage capacitor C1 and an external photovoltaic cell, wherein the energy storage capacitor C1 is connected with the external photovoltaic cell in parallel, and the anode and the cathode of the energy storage capacitor C1 are both connected with the ground.
The photovoltaic cell BT1 in fig. 2 outputs milliwatt level electric energy in working environment, and the energy storage circuit includes an energy storage capacitor C1 connected in parallel to two ends of BT1 for accumulating the milliwatt level electric energy converted from ambient light energy collected by the photovoltaic cell, and the effect is:
the voltage Vin across the energy storage capacitor C1 is equal to the output voltage of the photovoltaic cell, and Vin increases as the charge stored in the energy storage capacitor C1 increases. The high Vin voltage can make the output power of the photovoltaic cell high, so that the energy collection efficiency is high.
The energy storage capacitor C1 has low internal resistance and can provide continuous large current discharge, so that the energy storage capacitor C1 can drive the DC-DC conversion circuit with low input impedance to normally work after being connected with the photovoltaic cells in parallel.
The MOS field effect transistor M1 adopts a P-channel enhanced MOS field effect transistor, wherein the source electrode of the MOS field effect transistor M1 is connected with the anode of an energy storage capacitor C1; the drain electrode of the MOS field effect transistor M1 is the output end of the high-efficiency milliwatt photovoltaic energy collection control circuit; the gate of the MOS field effect transistor M1 is connected with a bias circuit.
Since the photovoltaic cell is a milliwatt output power, there are the following problems:
1. when the DC-DC conversion circuit works, the output power of the photovoltaic cell itself is usually lower than the input power of the DC-DC conversion circuit, and then the C1 will discharge outwards and cause the voltage across the terminals to gradually decrease.
2. If the control is not added, the voltage Vin at the two ends of the C1 is reduced until the Vin is equal to the under-voltage protection voltage of the DC-DC conversion circuit, at the moment, the DC-DC conversion circuit stops working, the photovoltaic cell charges the C1, and the Vin gradually rises.
3. Vin gradually rises and lets the DC-DC conversion circuit resume operation and again causes Vin to fall.
The processes 1, 2 and 3 are repeated all the time, the DC-DC conversion circuit keeps intermittent operation, but Vin always keeps near the protection voltage of the DC-DC conversion circuit, and the voltage is usually far lower than the optimal output voltage of the photovoltaic cell, so that the output power of the photovoltaic cell is very small, and the energy collection efficiency is low.
Therefore, the dual voltage control circuit of the present invention is used to solve the problem of low efficiency of energy collection caused by uncontrolled discharge of the energy storage capacitor C1, and has a specific structure as shown in fig. 2,
the bias circuit comprises a resistor R1 and a resistor R5, wherein one end of the resistor R1 is connected with the anode of the energy storage capacitor C1, the other end of the resistor R1 is connected with the resistor R5 in series, and the connection point of the resistor R1 and the resistor R5 is connected with the gate of the MOS field effect transistor M1
The conducting voltage control circuit comprises a Darlington composite tube formed by a triode T1 and a triode T2, a voltage division circuit formed by serially connecting a resistor R2 and a sliding resistor R3, and a resistor R4, wherein one end of the voltage division circuit formed by serially connecting a resistor R2 and a sliding resistor R3 is connected with the anode of the energy storage capacitor C1, and the other end of the voltage division circuit is grounded; the moving contact of the sliding resistor R3 is connected with the base electrode of the triode T1 through the resistor R4 and provides static operating point bias voltage for the triode T1 and the triode T2; the emitter of the triode T2 is connected with the ground; the collector of the triode T1 and the collector of the triode T2 are connected in parallel with the negative electrode of the diode D1; the anode of the diode D1 is connected with the resistor R5.
The turn-off voltage control circuit comprises a Darlington composite tube formed by a triode T3 and a triode T4, and a voltage division circuit formed by serially connecting a resistor R7 and a sliding resistor R8, wherein one end of the voltage division circuit formed by serially connecting a resistor R7 and a sliding resistor R8 is connected with the drain electrode of the MOS field effect tube M1, and the other end of the voltage division circuit is grounded; the moving contact of the sliding resistor R8 is connected with the base electrode of the triode T3 through the R6 and provides static operating point bias voltage for the triode T3 and the triode T4; the emitter of the triode T4 is grounded; the collector of the transistor T3 and the collector of the transistor T4 are connected in parallel with the cathode of the diode D2, and the anode of the diode D2 is connected with the resistor R5.
The transistors T1 and T2 are NPN silicon transistors, and have a V value when turned onBE(TH)About 0.6-0.7V, 0.6V is taken as an example for analysis. The no-load voltage of the photovoltaic cell BT1 commonly found in the market is generally higher than 3V and also higher than the undervoltage protection voltage of a DC-DC conversion circuit. When C1 is fully charged, Vin approaches the unloaded voltage of BT 1. M1 is P-channel enhancement type MOS FET with on-gate-source threshold voltage VGS(TH)Below 0V, i.e. when VG SBelow VGS(TH)At this time, M1 is on, when Vout is very close to equal Vin. On the contrary, when M1 is turned off, Vout is approximately equal to 0V, and the DC-DC conversion circuit does not work. The process of dual voltage control of the circuit is analyzed below.
State 1: as shown in FIG. 3, the controlled switch circuit and the on-state voltage control circuit of the present invention realize the on-state voltage VOnAnd (4) controlling. In fig. 3, Vin is divided by R2 and R3, and the output voltage of R3 moving contact is applied to the base of transistor T1 by R4, and the voltage is VbT1,VbT1Increasing as Vin increases. T1 and T2 form a Darlington composite tube when Vin increases to V or moreOnWhen is equal to VbT1Also increased by 2 times VBE(TH)I.e., 1.2V, T1 and T2 are in the on state. At this time, current ID1Greater than 0, a loop is formed from the Vin end to the GND end through R1, R5, D1, T1 and T2, as shown by the dotted arrow in FIG. 3. The voltage drop across R1 results in VG S <0. The resistance values of R2, R3, R4, R1 and R5 are reasonably designed, and the position of the movable contact of R3 can be adjusted, so that the following conditions are met: vin increases to equal to or greater than VOnWhen, VGSBelow VGS(TH)And if so, M1 is conducted, Vout is approximately equal to Vin and higher than the under-voltage protection voltage of the DC-DC conversion circuit, and the DC-DC conversion circuit works normally.
State 2: as shown in FIG. 4, the controlled switch circuit and the turn-off voltage control circuit of the present invention realize the turn-off voltage VOffAnd (4) controlling. Once M1 is turned on, Vout is approximately equal to Vin, and the DC-DC converter operates normally. Meanwhile, the Vout voltage is divided by R7 and R8, and the output voltage of the R8 moving contact is divided byR6 is applied to the base of transistor T3 at voltage VbT3. The resistance values of R7 and R8 are reasonably designed, and the movable contact position of R8 is adjustable, so that VbT3Greater than 2 times VBE(TH)That is, 1.2V is established, T3 and T4 are turned on. At this time, current ID2Greater than 0, a loop is formed from the Vin end to the GND end through R1, R5, D2, T3 and T4, as shown by the dotted arrow in FIG. 4. The voltage drop across R1 results in VG S <0. The resistance values of R6, R7, R8, R1 and R5 are reasonably designed, and the position of the movable contact of R6 can be adjusted, so that the following conditions are met: vout is equal to or greater than VOffWhen, VG SBelow VGS(TH)And if so, M1 is conducted, and at the moment, Vout is approximately equal to Vin and higher than the under-voltage protection voltage of the DC-DC conversion circuit, and the DC-DC conversion circuit works normally. In addition, the circuit parameter is designed as VOn- VOff > |VTHI is true, | VTHAnd | is the hysteresis width voltage.
State 3: fig. 5 is a controlled switching circuit, an on-voltage control circuit, and an off-voltage control circuit of the present invention. M1 is in conducting state, and the DC-DC conversion circuit works normally. The input power of the DC-DC conversion circuit is larger than the output power of the photovoltaic cell, which causes the voltage Vout to gradually decrease, M1 is in a conducting state, Vin is also gradually decreased, and Vb is causedT1And decreases. When Vb isT1Less than 2 times VBE(TH)I.e., 1.2V, T1 and T2 are cut off, and the current ID1Equal to 0 as shown in fig. 5.
At this time, since Vout is still true at Voff or higher, T3 and T4 are kept on and the current ID2Greater than 0, VG SBelow VGS(TH)If this is always true, M1 is always on, Vout is close to equal to Vin, and the DC-DC converter operates normally, as shown in fig. 5.
And 4: the normal operation of the DC-DC conversion circuit causes the Vout voltage to further gradually decrease, causing VbT3And decreases. When Vout is reduced to VOffAt this time VbT3Just less than 2 times VBE(TH)I.e., 1.2V, T3 and T4 are cut off. At this time, T1, T2, T3 and T4 are all cut off, and V of M1 isG SEqual to 0V, M1 is switched from on to off, and the DC-DC converter circuit stops operating.
And state 5: the photovoltaic cell continues to charge the C1 of the tank circuit. The R2 and R3 are designed as high-resistance resistors, the current flowing through R2 is lower than 10 microamperes, the current is far lower than the output current (milliampere level) of the photovoltaic cell, and the voltage across the C1 gradually increases. Until Vin increases to V or moreOnWhen this happens, state 5 jumps to state 1.
From the above 5 state change processes it can be seen that: the voltage across C1 rises to VOnWhen M1 is conducted, the DC-DC conversion circuit works normally, and simultaneously the voltage across C1 gradually drops, but M1 can still be kept conducted. Until the voltage across C1 is lower than VOffAt this time, M1 is turned off, and the DC-DC converter circuit stops operating. The photovoltaic cell continues to charge C1 and causes the voltage across C1 to rise until V or moreOnAnd entering the next working period of the DC-DC conversion circuit. Therefore, the input voltage of the DC-DC conversion circuit always works at VOff VOn]In the range, the voltage is far higher than the under-voltage protection voltage of the DC-DC conversion circuit, so that the circuit can obtain high energy conversion efficiency of the photovoltaic cell.
The transistors T1-T4 and the MOS transistor M1 in the invention adopt low-power consumption devices, and the static power consumption is very low when the MOS transistor works in a switch state; the resistors R1-R8 are all high resistance parameters, for example, the current passing through R2 and R7 is less than 10 microamperes, ID1And ID2Below 10 microamperes, the current of these branches is much lower than the output current of the photovoltaic cell (in milliamperes), so the static power consumption of the control circuit is very low.
The principle and the implementation mode of the invention are explained by applying specific embodiments in the invention, and the description of the embodiments is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.
It will be appreciated by those of ordinary skill in the art that the embodiments described herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited embodiments and examples. Those skilled in the art can make various other specific changes and combinations based on the teachings of the present invention without departing from the spirit of the invention, and these changes and combinations are within the scope of the invention.