DC-DC booster circuit with high step-up ratio
阅读说明：本技术 一种高升压比dc-dc升压电路 (DC-DC booster circuit with high step-up ratio ) 是由 白杰 郑文会 何耀军 于 2021-07-30 设计创作，主要内容包括：本发明涉及一种升压电路,具体涉及一种高升压比DC-DC升压电路,克服传统BOOST升压电路及非隔离Boost升压变换器无法实现高升压比的问题。本发明将包括BOOST升压电路与二极管电荷泵电路相结合,通过电感存储及释放能量与电容充放电组成的二级储能方式,在给定很小的输入电压下,就可实现由小电压升至高电压,升压比可达40左右,有效的提升了电压升压比。相对传统DC-DC升压芯片与非隔离Boost升压变换器,本发明升压电路具有较高升压比,相对反激式升压电路,本发明升压电路体积小,输出电压波纹小。(The invention relates to a BOOST circuit, in particular to a high BOOST ratio DC-DC BOOST circuit, which solves the problem that the traditional BOOST circuit and a non-isolated BOOST converter cannot realize the high BOOST ratio. The BOOST circuit is combined with the diode charge pump circuit, and the BOOST ratio can be increased from a small voltage to a high voltage by a two-stage energy storage mode consisting of inductive energy storage and release and capacitive charge and discharge under a given very small input voltage, and can reach about 40, so that the voltage BOOST ratio is effectively increased. Compared with the traditional DC-DC booster chip and non-isolated Boost converter, the Boost circuit has higher Boost ratio, and compared with the flyback Boost circuit, the Boost circuit has small volume and small output voltage ripple.)
1. A high step-up ratio DC-DC boost circuit, characterized in that: the BOOST circuit comprises a BOOST circuit and a diode charge pump circuit;
the BOOST circuit comprises a DC-DC BOOST chip, an inductor L1, a resistor R1, a resistor R2, an input filter capacitor C9 and an output filter capacitor C10;
a VIN pin of the DC-DC booster chip is connected with a power supply input;
one end of the inductor L1 is connected with a VIN pin of the DC-DC boost chip, and the other end of the inductor L1 is connected with a SW pin of the DC-DC boost chip;
the diode charge pump circuit is connected between the SW pin of the DC-DC boost chip and the load in series, and the diode charge pump circuit is charged and discharged through the inductor L1 and the SW pin of the DC-DC boost chip, so that the voltage ratio is improved;
one end of the resistor R1 is connected with the output end of the diode charge pump circuit, the other end of the resistor R1 is connected with one end of the resistor R2, and the other end of the resistor R2 is grounded;
the common end of the resistor R1 and the resistor R2 is connected to the FB pin of the DC-DC boost chip;
one end of the input filter capacitor C9 is connected with the power input, and the other end is grounded;
one end of the output filter capacitor C10 is connected with the output end of the diode charge pump circuit, and the other end is grounded.
2. The high step-up ratio DC-DC boost circuit of claim 1, wherein: the diode charge pump circuit comprises N diodes and N-1 capacitors, wherein N is an integer greater than or equal to 2;
n diodes are sequentially connected in series, the anode of the diode D1 is connected with the SW pin of the DC-DC boost chip, and the diode DNThe negative electrode of the resistor is connected with one end of a resistor R1;
each capacitor is respectively bridged at two ends of two adjacent diodes; one end of the capacitor C1 is connected with the SW pin of the DC-DC boost chip, and the other end is connected with the cathode of the diode D2; one end of the capacitor C2 is connected with the anode of the diode D2, and the other end is connected with the diodeThe negative electrode of D3 is connected; by analogy, the capacitor CN-1And a diode DN-1Is connected with the anode of the diode D, and the other end of the diode D is connected with the anode of the diodeNAre connected with each other.
3. The high step-up ratio DC-DC boost circuit of claim 2, wherein: the withstand voltage values of the capacitors are equal.
4. The high step-up ratio DC-DC boost circuit of claim 3, wherein: the DC-DC boost chip is packaged by SOT23-5, N diodes and integrated SOT 23-6.
5. The high step-up ratio DC-DC boost circuit according to any of claims 1-4, wherein: the circuit also comprises an operational amplifier U2, a resistor R3 and a resistor R4; the forward input end of the operational amplifier U2 is connected with the end where the resistor R1 and the resistor R2 are connected in common, the reverse input end is connected with the DAC interface of the controller through the resistor R3, and the output end is connected with the FB pin of the DC-DC boost chip; a resistor R4 is connected across the output and inverting input of the op-amp U2.
6. The high step-up ratio DC-DC boost circuit of claim 5, wherein:
and the operational amplifier package is packaged by SOT 23-5.
7. The high step-up ratio DC-DC boost circuit of claim 1, wherein: the diode charge pump circuit comprises N diodes and N-1 capacitors, wherein N is an integer greater than or equal to 2;
n diodes are sequentially connected in series, the anode of the diode D1 is connected with the SW pin of the DC-DC boost chip, and the diode DNThe negative electrode of the resistor is connected with one end of a resistor R1;
one end of each capacitor is connected between two adjacent diodes respectively, and the other end is grounded.
8. The high step-up ratio DC-DC boost circuit of claim 7, wherein: capacitor COne end of the capacitor C2 is connected between the diode D2 and the diode D3, and so on, and the capacitor C is connected between the diode D1 and the diode D2N-1Is connected to the diode DN-1And diode DNTo (c) to (d); capacitor C1, capacitor C2 … and capacitor CN-1The voltage withstanding value and the voltage boosting multiple are correspondingly and sequentially boosted;
the DC-DC boost chip is packaged by SOT23-5, N diodes and integrated SOT 23-6.
9. The high step-up ratio DC-DC boost circuit according to claim 7 or 8, wherein: the circuit also comprises an operational amplifier U2, a resistor R3 and a resistor R4; the forward input end of the operational amplifier U2 is connected with the end where the resistor R1 and the resistor R2 are connected in common, the reverse input end is connected with a DAC interface of the controller through the resistor R3, and the output end is connected with a FB port of the DC-DC boost chip; a resistor R4 is connected across the output and inverting input of the op-amp U2.
10. The high step-up ratio DC-DC boost circuit of claim 9, wherein: the DC-DC booster chip and the operational amplifier package are packaged by SOT23-5, and the N diodes are packaged by integrated SOT 23-6.
Technical Field
The invention relates to a boost circuit, in particular to a high boost ratio DC-DC boost circuit.
Background
The BOOST circuit is a common switching direct current BOOST circuit, and controls inductance to store and release energy through the on and off of a switching device, so that the output voltage is higher than the input voltage, and the BOOST is realized.
At present, BOOST conversion can be realized by adjusting the duty ratio of a DC-DC BOOST chip in a BOOST circuit, and the BOOST ratio can theoretically change within the range of 1 to infinity, but with the increase of the duty ratio, the reverse recovery loss of a diode and the switching loss of a switching tube are increased, so that the system efficiency is reduced, and in practical application, the BOOST ratio of the BOOST chip is generally about 4, so that the requirement of a device for high BOOST ratio cannot be met. The traditional high step-up ratio direct current conversion device is a non-isolated Boost converter, and on the occasion of high output voltage, a high input-output voltage ratio cannot be achieved due to the influence of parasitic parameters.
Another conventional dc converter with a high step-up ratio is a FlyBack boost circuit, that is, a commonly-known FlyBack boost circuit, which can achieve a high step-up ratio, but needs a transformer and an isolation device, resulting in a large circuit size and a large output voltage ripple, and in those applications where isolation is not required or the size requirement is small, boosting through the transformer is not a good choice.
Disclosure of Invention
In order to solve the problem that the traditional BOOST circuit and a non-isolated BOOST converter cannot realize a high BOOST ratio, the invention provides a high BOOST ratio DC-DC BOOST circuit by combining the BOOST circuit and a charge pump circuit. Compared with the traditional DC-DC booster chip and non-isolated Boost converter, the Boost circuit has higher Boost ratio, and compared with the flyback Boost circuit, the Boost circuit has small volume and small output voltage ripple.
The technical scheme of the invention provides a DC-DC booster circuit with a high step-up ratio, which is characterized in that: the BOOST circuit comprises a BOOST circuit and a diode charge pump circuit;
the BOOST circuit comprises a DC-DC BOOST chip, an inductor L1, a resistor R1, a resistor R2, an input filter capacitor C9 and an output filter capacitor C10;
the VIN pin of the DC-DC booster chip is connected with the power input;
one end of the inductor L1 is connected with a VIN pin of the DC-DC boost chip, and the other end of the inductor L1 is connected with a SW pin of the DC-DC boost chip;
the diode charge pump circuit is connected between the SW pin of the DC-DC boost chip and the load in series, and the diode charge pump circuit is charged and discharged through the inductor L1 and the SW pin of the DC-DC boost chip, so that the voltage ratio is improved;
one end of the resistor R1 is connected with the output end of the diode charge pump circuit, the other end of the resistor R1 is connected with one end of the resistor R2, and the other end of the resistor R2 is grounded;
the common end of the resistor R1 and the resistor R2 is connected to the FB pin of the DC-DC boost chip;
one end of the input filter capacitor C9 is connected with the power input, and the other end is grounded;
one end of the output filter capacitor C10 is connected with the output end of the diode charge pump circuit, and the other end is grounded.
Further, the diode charge pump circuit comprises N diodes and N-1 capacitors, wherein N is an integer greater than or equal to 2;
n diodes are sequentially connected in series, the anode of the diode D1 is connected with the SW pin of the DC-DC boost chip, and the diode DNThe negative electrode of the resistor is connected with one end of a resistor R1;
each capacitor is respectively bridged at two ends of two adjacent diodes; one end of the capacitor C1 is connected with the SW pin of the DC-DC boost chip, and the other end is connected with the cathode of the diode D2; one end of the capacitor C2 is connected with the anode of the diode D2, and the other end is connected with the cathode of the diode D3; by analogy, the capacitor CN-1And a diode DN-1Is connected with the anode of the diode D, and the other end of the diode D is connected with the anode of the diodeNAre connected with each other.
When the SW pin of the DC-DC boost chip is at a low level, the power supply stores energy to the inductor L1, when the SW pin of the DC-DC boost chip is switched to a high level, the inductor L1 releases the energy, the capacitor C1 is charged through the pin which is commonly connected with the capacitor C1, and the diodes D1 to DNForward biasing and charging a capacitor across the two ends of the diode; when the SW is switched to the low level again, the inductor stores energy, and due to the unidirectional conductivity of the diode, the voltage at two ends of the capacitor cannot change suddenly, so that the voltage at one end of the capacitor C1 connected with the cathode of the diode D2 adds electricity to the energy released by the inductorThe voltage of the end, connected with the cathode of the diode D1, of the capacitor C2 is the energy released by the inductor plus the power voltage, and the voltage of the end, connected with the cathode of the diode D3, of the capacitor C2 is increased by a certain multiple; by analogy, every two diodes, the voltage can be increased by a certain multiple; the BOOST output voltage is boosted through the charge pump, so that the output of the BOOST circuit is boosted by a certain multiple compared with the original output, and the BOOST efficiency is not influenced.
Further, the specifications of the capacitors are kept consistent, that is, the capacitor withstand voltage values are equal.
Further, in order to reduce the size, the DC-DC boost chip is packaged by SOT23-5, N diodes and an integrated SOT 23-6.
Furthermore, in order to realize accurate real-time voltage regulation, the boost circuit further comprises an operational amplifier U2, a resistor R3 and a resistor R4; the forward input end of the operational amplifier U2 is connected with the joint end of a resistor R1 and a resistor R2, the reverse input end is connected with a DAC interface of the controller through a resistor R3, and the output end is connected with an FB pin of the DC-DC boost chip; a resistor R4 is connected across the output and inverting input of the op-amp U2.
In order to further reduce the size of the booster circuit, the operational amplifier package can be selected from packages such as SOT 23-5.
Furthermore, the diode charge pump circuit can also select a circuit structure different from the circuit structure, wherein the circuit structure comprises N diodes and N-1 capacitors, and N is an integer greater than or equal to 2; n diodes are sequentially connected in series, the anode of the diode D1 is connected with the SW pin of the DC-DC boost chip, and the diode DNThe negative electrode of the resistor is connected with one end of a resistor R1;
one end of each capacitor is connected between two adjacent diodes respectively, and the other end is grounded.
The capacitor is charged and discharged through the inductor and the SW pin of the DC-DC boost chip, so that the voltage is boosted; when the SW pin of the DC-DC boost chip is at a low level, the power supply stores energy to the inductor L1, and when the SW pin of the DC-DC boost chip is switched to a high level, the inductor L1 releases the energy, and the diodes D1 to DNForward biasing and charging a capacitor behind the diode; SW again switches to LowWhen the capacitor is in a level state, the inductor stores energy, and because of the unidirectional conductivity of the diode, the voltage at two ends of the capacitor cannot change suddenly, so that the voltage at one end of the capacitor C1 connected with the cathode of the diode D1 is the sum of the energy released by the inductor and the power supply voltage, the voltage at one end of the capacitor C2 connected with the cathode of the diode D2 is the sum of the energy released by the inductor and the power supply voltage, and the voltage at one end of the capacitor C3 connected with the cathode of the diode D3 is increased by a certain multiple; by analogy, every two diodes, the voltage can be increased by a certain multiple; the BOOST output voltage is boosted through the charge pump, so that the output of the BOOST circuit is boosted by a certain multiple compared with the original output, and the BOOST efficiency is not influenced.
Further, one end of the capacitor C1 is connected between the diode D1 and the diode D2, one end of the capacitor C2 is connected between the diode D2 and the diode D3, and so on, and the capacitor C1N-1Is connected to the diode DN-1And diode DNTo (c) to (d); capacitor C1, capacitor C2 … and capacitor CN-1The voltage withstanding value and the voltage boosting multiple are correspondingly and sequentially boosted; the withstand voltage of the capacitor is generally selected to be about 1.5 times of the actual voltage. The DC-DC boost chip is packaged by SOT23-5, N diodes and integrated SOT 23-6.
Furthermore, in order to realize accurate real-time voltage regulation, the boost circuit further comprises an operational amplifier U2, a resistor R3 and a resistor R4; the forward input end of the operational amplifier U2 is connected with the end where the resistor R1 and the resistor R2 are connected in common, the reverse input end is connected with a DAC interface of the controller through the resistor R3, and the output end is connected with a FB port of the DC-DC boost chip; a resistor R4 is connected across the output and inverting input of the op-amp U2.
In order to further reduce the size of the booster circuit, the operational amplifier package can be selected from a package such as SOT 23-5.
The invention has the beneficial effects that:
1. according to the invention, the BOOST circuit is combined with the charge pump circuit, and the BOOST ratio can be increased from a small voltage to a high voltage by a two-stage energy storage mode consisting of inductive energy storage and release and capacitive charge and discharge under a given very small input voltage, so that the BOOST ratio can reach about 40, and the voltage BOOST ratio is effectively increased.
2. The BOOST booster circuit and the charge pump circuit adopted by the invention have smaller volumes, the SOT23-5 can be realized by the current DC-DC booster chip and the operational amplifier package, even smaller, the size of the whole circuit can be very small by selecting the device type integrating a plurality of diodes and adding a limited resistor-capacitor-inductor discrete device, the space on a board is saved, the output voltage ripple is small, and the cost of the required device is controllable.
3. In the application process of the high-voltage driving MEMS galvanometer, due to frequency drift and other reasons, the amplitude and the phase of the galvanometer are slightly shifted, at the moment, the driving voltage needs to be finely adjusted, so that the vibration position of the galvanometer is slightly changed, the slight shift of the amplitude and the phase is further compensated, and the galvanometer works at an expected position. This is typically achieved by varying the external voltage-dropping resistance of the DC-DC boost chip. However, frequent replacement of the resistor is time and labor consuming, and it is not always possible to find a suitable resistor to regulate the desired voltage; for small voltage adjustments, it is difficult to achieve the desired goal even when the resistance accuracy is not sufficient; meanwhile, in the working process of the galvanometer, the resistor cannot be replaced, so that the voltage cannot be adjusted in real time according to requirements.
The invention combines the BOOST booster circuit and the charge pump circuit, adds the operational amplifier, and under the condition of selecting the DC-DC booster chip, the V of the chipfbIs constant, and selects proper R1, R2, R3 and R4, namely R1, R2, R3 and R4 which are known quantitives, so that the output voltage V of the booster circuit can be changed by adjusting the value of the DAC controlleroutThe high step-up ratio can be realized, and the purpose of dynamically regulating the output voltage can be achieved.
Drawings
FIG. 1 is a DC-DC boost circuit according to a first embodiment;
FIG. 2 is a DC-DC booster circuit according to a second embodiment;
FIG. 3 is a DC-DC booster circuit according to a third embodiment;
FIG. 4 is a DC-DC booster circuit according to a fourth embodiment;
FIG. 5 is a simplified controller interface;
FIG. 6 is a waveform diagram of the DC-DC boost circuit according to the first embodiment;
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, specific embodiments accompanied with figures are described in detail below, and it is apparent that the described embodiments are a part of the embodiments of the present invention, not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making creative efforts based on the embodiments of the present invention, shall fall within the protection scope of the present invention.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than those specifically described and will be readily apparent to those of ordinary skill in the art without departing from the spirit of the present invention, and therefore the present invention is not limited to the specific embodiments disclosed below.
Furthermore, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one implementation of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.
Furthermore, the present invention is described in detail with reference to the drawings, and when the embodiments of the present invention are described in detail, the drawings are only for illustrative purposes and should not be construed as limiting the scope of the present invention. In addition, the three-dimensional dimensions of length, width and depth should be included in the actual fabrication.
Also in the description of the present invention, it should be noted that the terms "first, second or nth" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The terms "connected" and "coupled" are used broadly and encompass both mechanical, electrical, or direct connections, indirect connections through intermediaries, and communication between two elements, unless expressly specified or limited otherwise. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Example one
As can be seen from FIG. 1, the high step-up ratio DC-DC BOOST circuit of the present embodiment includes a BOOST circuit and a diode charge pump circuit. In the present embodiment, the diode charge pump circuit includes 8 diodes and 7 cross-over capacitors; in other embodiments, an appropriate number of diodes may be selected according to the target voltage required at the load end. In this embodiment, the voltage of the cathode of the diode connected to the SW pin of the DC-DC boost chip can be doubled every time two diodes and two capacitors are added. The BOOST circuit of the embodiment includes a DC-DC BOOST chip U1, an inductor L1, feedback resistors R1 and R2, an input filter capacitor C9, and an output filter capacitor C10.
One end of the input filter capacitor C9 is connected with the power input, and the other end is grounded; and one end of the output filter capacitor C10 is connected with the output end of the diode charge pump circuit, and the other end of the output filter capacitor C10 is grounded. One end of the inductor L1 is connected to the VIN pin of the DC-DC boost chip U1, and the other end is connected to the SW pin of the DC-DC boost chip U1. One end of the resistor R1 is connected with the output end of the diode charge pump circuit, the other end of the resistor R1 is connected with one end of the resistor R2, and the other end of the resistor R2 is grounded; the common end of the resistor R1 and the resistor R2 is connected to the FB pin of the DC-DC boost chip.
Diodes D1 to D8 are connected in series in sequence and then are connected between the SW pin of the DC-DC boost chip and the load in series; as can be seen from fig. 1, the anode of the diode D1 is connected to the SW pin of the DC-DC boost chip, the cathode is connected to the anode of the diode D2, the cathode of the diode D2 is connected to the anode of the diode D3, and so on, the anode of the diode D8 is connected to the cathode of the diode D7, and the cathode is connected to one end of the resistor R1.
Across capacitors C1 to C7, across diodes D1 to D8; as can be seen from fig. 1, one end of the across capacitor C1 is connected to the SW pin of the DC-DC boost chip, and the other end is connected to the cathode of the diode D2, that is, the capacitor C1 is connected across the diodes D1 and D2; one end of a cross-over capacitor C2 is connected with the anode of the diode D2, and the other end is connected with the cathode of the diode D3, namely, the capacitor C2 is connected across the diodes D2 and D3; by analogy, the cross-over capacitor C7 is connected to the anode of the diode D7, and the other end is connected to the cathode of the diode D8, i.e., connected across the diodes D7 and D8.
The specific working principle of the circuit is as follows:
the BOOST circuit charges and discharges a diode charge pump circuit through an inductor energy storage pin and a SW switch pin, when the SW pin of the DC-DC BOOST chip is at a low level, a power supply stores energy to an inductor L1, when the SW pin of the DC-DC BOOST chip is switched to a high level, the inductor L1 releases energy, the capacitor C1 is charged through a pin which is commonly connected with a capacitor C1, and the diodes D1 to DNForward biasing and charging a capacitor across the two ends of the diode; when the SW is switched to the low level again, the inductor stores energy, and because of the one-way conductivity of the diode, the voltage at two ends of the capacitor can not change suddenly, so that the voltage at one end of the capacitor C1 connected with the cathode of the diode D2 is the voltage at the end connected with the cathode of the diode D2 and is the energy released by the inductor plus the power supply voltage, the voltage at one end connected with the cathode of the capacitor C2 connected with the cathode of the diode D1 is the energy released by the inductor plus the power supply voltage, and the voltage at one end connected with the cathode of the capacitor C2 and the cathode of the diode D3 is increased by a certain multiple; by analogy, every two diodes, the voltage can be increased by a certain multiple; as shown in fig. 6, which is a waveform diagram of the DC-DC boost circuit of this embodiment, a waveform indicated by reference numeral 1 in the diagram is a voltage waveform of a terminal at which the capacitor C2 is connected to the negative electrode of the diode D1, a waveform indicated by reference numeral 2 is a voltage waveform of a terminal at which the capacitor C1 is connected to the negative electrode of the diode D2, a waveform indicated by reference numeral 3 is a voltage waveform of a terminal at which the capacitor C2 is connected to the negative electrode of the diode D3, and a waveform indicated by reference numeral 4 is a voltage waveform of a terminal at which the capacitor C3 is connected to the negative electrode of the diode D4.
The BOOST output voltage is boosted through the charge pump, so that the output of the BOOST circuit is boosted by a certain multiple compared with the original output, and the BOOST efficiency is not influenced. The output voltage of the diode charge pump circuit is detected by the FB pin of the DC-DC boost chip.
The specific calculation of the output voltage is as follows:
Vout＝Vfb*(1+R1/R2)
example two
As shown in fig. 2, in this embodiment, on the basis of the first embodiment, an operational amplifier U2 and resistors R3 and R4 are added to the FB pin of the DC-DC boost chip;
as can be seen from fig. 2, the forward input end of the operational amplifier U2 is connected to the end where R1 and R2 are commonly connected, the reverse input end is connected to the DAC interface of the controller (the DAC interface of the controller shown in fig. 5 may be used), the output end is connected to the FB pin of the DC-DC boost chip, the resistor R3 is connected in series between the reverse input end and the DAC interface of the controller, and the resistor R4 is connected across the output end and the reverse input end of the operational amplifier, where the reverse input end is connected to the end of the resistor R3 close to the reverse input end.
By combining the operational amplifier characteristics, the output voltage V of the circuit after the operational amplifier is increased can be deducedoutComprises the following steps:
Vout＝(1+R1/R2)*(Vfb+Vdac*R4/R3)/(1+R4/R3)
v of chip under the condition of selecting DC-DC boost chipfbIs constant, and selects proper R1, R2, R3 and R4, namely R1, R2, R3 and R4 which are known quantitives, so that the output voltage V of the booster circuit can be changed by adjusting the value of DACoutThe purpose of regulating the output voltage is achieved. At input of 5V, VfbUnder the condition of 1.23V, if R1-1M, R2-10.5K, R3-12K and R4-10K are selected, then V isout＝43.74*Vdac+ 64.567; by adjusting VdacThe maximum output voltage can be more than 200V, the boost ratio can reach about 40, and the voltage boost ratio is effectively improved.
In the prior art, both a DC-DC boost chip and an operational amplifier package can be SOT23-5 or even smaller, although the number of discrete diodes is large, the device type of integrating a plurality of diodes can be selected, integrated SOT23-6 and other small packages can be selected, and a limited resistance capacitance inductance discrete device is added, so that the size of the whole circuit can be small, and the space on a board is saved.
EXAMPLE III
As shown in fig. 3, the present embodiment adopts a diode charge pump circuit different from the first and second embodiments, and the diode charge pump circuit of the present embodiment also includes 8 diodes and 7 capacitors; in other embodiments, an appropriate number of diodes may be selected according to the target voltage required at the load end. In this embodiment, the voltage of the cathode of the diode connected to the SW pin of the DC-DC boost chip can be doubled every time two diodes and two capacitors are added. The BOOST circuit of the present embodiment is the same as the first embodiment, and includes a DC-DC BOOST chip U1, an inductor L1, feedback resistors R1 and R2, an input filter capacitor C9, and an output filter capacitor C10.
One end of the input filter capacitor C9 is connected with the power input, and the other end is grounded; and one end of the output filter capacitor C10 is connected with the output end of the diode charge pump circuit, and the other end of the output filter capacitor C10 is grounded. One end of the inductor L1 is connected to the VIN pin of the DC-DC boost chip U1, and the other end is connected to the SW pin of the DC-DC boost chip U1. One end of the resistor R1 is connected with the output end of the diode charge pump circuit, the other end of the resistor R1 is connected with one end of the resistor R2, and the other end of the resistor R2 is grounded; the common end of the resistor R1 and the resistor R2 is connected to the FB pin of the DC-DC boost chip.
Diodes D1 to D8 are connected in series in sequence and then are connected between the SW pin of the DC-DC boost chip and the load in series; as can be seen from fig. 3, the anode of the diode D1 is connected to the SW pin of the DC-DC boost chip, the cathode is connected to the anode of the diode D2, the cathode of the diode D2 is connected to the anode of the diode D3, and so on, the anode of the diode D8 is connected to the cathode of the diode D7, and the cathode is connected to one end of the resistor R1.
One ends of the capacitors C1 to C7 are respectively connected between two adjacent diodes, and the other ends of the capacitors are all grounded, so that another charge pump circuit is formed, and the same effect can be achieved.
The specific working principle of the circuit is as follows:
when the SW pin of the DC-DC boost chip is at a low level, the power supply stores energy to the inductor L1, and when the SW pin of the DC-DC boost chip is switched to a high level, the inductor L1 releases the energy, and the diodes D1 to DNForward biasing and charging a capacitor behind the diode; when the SW is switched to the low level again, the inductor stores energy, and the voltage at two ends of the capacitor cannot change suddenly due to the unidirectional conductivity of the diode, so that the power is suppliedThe voltage of one end of the capacitor C1 connected with the cathode of the diode D1 is the energy released by the inductor plus the power supply voltage, the voltage of one end of the capacitor C2 connected with the cathode of the diode D2 is the energy released by the inductor plus the power supply voltage, and the voltage of one end of the capacitor C3 connected with the cathode of the diode D3 is increased by a certain multiple; by analogy, every two diodes, the voltage can be increased by a certain multiple; the BOOST output voltage is boosted through the charge pump, so that the output of the BOOST circuit is boosted by a certain multiple compared with the original output, and the BOOST efficiency is not influenced.
The output voltage of the diode charge pump circuit is detected by the FB pin of the DC-DC boost chip. The calculation of the output voltage is the same as in the first embodiment.
Example four
As shown in fig. 4, in this embodiment, on the basis of the third embodiment, an operational amplifier U2 and resistors R3 and R4 are added to the FB pin of the DC-DC boost chip;
as can be seen from fig. 4, the forward input of the operational amplifier U2 is connected to the end where R1 and R2 are commonly connected, the reverse input end is connected to the DAC interface of the controller, the output end is connected to the FB pin of the DC-DC boost chip, the resistor R3 is connected in series between the reverse input end and the DAC interface of the controller, and R4 is connected across the output and reverse input ends of the operational amplifier, wherein the reverse input end connection point is the end of the resistor R3 close to the reverse input end.
By combining the operational amplifier characteristics, the output voltage V of the circuit after the operational amplifier is increased can be deducedoutComprises the following steps:
Vout＝(1+R1/R2)*(Vfb+Vdac*R4/R3)/(1+R4/R3)
v of chip under the condition of selecting DC-DC boost chipfbIs constant, and selects proper R1, R2, R3 and R4, namely R1, R2, R3 and R4 which are known quantitives, so that the output voltage V of the booster circuit can be changed by adjusting the value of DACoutThe purpose of regulating the output voltage is achieved. At input of 5V, VfbUnder the condition of 1.23V, if R1-1M, R2-10.5K, R3-12K and R4-10K are selected, then V isout＝43.74*Vdac+ 64.567; by adjusting VdacThe value of (2) can ensure that the maximum output voltage is more than 200V, the boost ratio can reach about 40, and the effective boost is realizedThe voltage boosting ratio is boosted.
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