Pulse-controlled booster circuit

Abstract

The utility model discloses a pulse-controlled boost circuit, which comprises a pulse generation unit, a push-pull output unit and a bootstrap boost unit which are connected in sequence, and is characterized in that the pulse generation unit comprises an oscillation resistor R1, a threshold resistor R2, a threshold resistor R3, a charging resistor R4, a positive feedback resistor R5, a comparator U1, an oscillation capacitor C2 and a filter capacitor C3 which are connected; the push-pull output unit comprises a driving triode Q1 and a driving triode Q2; the bootstrap boost unit comprises an isolation diode D1 and a bootstrap capacitor C1. According to the pulse-controlled booster circuit, an energy storage inductor is not used, the occupied space is small and the height is low when the PCB is arranged, the miniaturization standard required by the current market is met, and the application range is wide. Meanwhile, the booster circuit is built by using the operational amplifiers, the circuit is easy to realize, and the selectable operational amplifiers have multiple models.

Description

Technical Field

[0001] The utility model relates to the technical field of switch power supplies, in particular to a pulse-controlled boost circuit. Background Art

[0002] With the rapid development of electronic technology, the demand for DC-DC power supplies is increasing, and the performance requirements are also getting higher and higher. Miniaturized, portable, high-efficiency, and fully domestically produced power supply equipment has become a new market trend. In order to be more widely used in various environments and various electronic devices, product miniaturization needs to be solved from all aspects of the power circuit.

[0003] In the DC-DC power supply circuit, the conventional boost circuit is the Boost boost circuit, which is composed of an energy storage inductor, a switch tube and a rectifier diode. It controls the inductor to store and release energy by turning the switch tube on and off, so that the output voltage is higher than the input voltage. This method is relatively common. In order to achieve the purpose of converting low voltage into high voltage, the Boost boost circuit often uses a larger energy storage inductor to store energy, which occupies a large space. At the same time, there are few low-voltage Boost boost chips, which is not easy to produce domestically, and does not meet the new market trend of miniaturization, portability and domestic production of products.

[0004] From the above, it is urgent to design a boost circuit that occupies a small space and has a large number of optional op amp models. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the utility model is to provide a simple pulse-controlled boost circuit to solve the problems of large space occupied by energy storage inductors and few optional chips in the existing Boost circuit.

[0006] In order to solve the above technical problems, the utility model adopts the following technical solutions:

[0007] A pulse-controlled boost circuit comprises a pulse generating unit, a push-pull output unit and a bootstrap boost unit connected in sequence, wherein:

[0008] The pulse generating unit comprises an oscillating resistor R1, a threshold resistor R2, a threshold resistor R3, a charging resistor R4, a positive feedback resistor R5, a comparator U1, an oscillating capacitor C2 and a filtering capacitor C3; wherein one end of the threshold resistor R3 is connected to one end of the filtering capacitor C3, pin 5 of the voltage comparator U1 and one end of the charging resistor R4, and the connection point is connected to the VIN+ terminal as the input end of the pulse generating unit; the other end of the resistor R3 is connected to one end of the threshold resistor R2, one end of the positive feedback resistor R5 and pin 4 of the voltage comparator U1; the other end of the threshold resistor R2 is connected to one end of the oscillating capacitor C2 and pin 2 of the voltage comparator U1, and the connection point is grounded; the other end of the positive feedback resistor R5 is connected to the other end of the charging resistor R4, one end of the oscillating resistor R1 and the output end (pin 1) of the voltage comparator, and the connection point is connected to the second input end of the push-pull output unit as the output end of the pulse generating unit; the other end of the oscillating resistor R1 is respectively connected to pin 3 of the voltage comparator U1 and one end of the oscillating capacitor C2;

[0009] The push-pull output unit includes a driving transistor Q1 and a driving transistor Q2; wherein the collector of the driving transistor Q1 is grounded, and its base is connected to the base of the driving transistor Q2, and the connection point is connected to the output end of the pulse generating unit as the second input end of the push-pull output unit; the emitter of the driving transistor Q1 is connected to the emitter of the driving transistor Q2, and the connection point is connected to the second input end of the bootstrap boosting unit as the output end of the push-pull output unit; the collector of the driving transistor Q2 is connected to the VIN+ terminal as the first input end of the push-pull output unit.

[0010] The bootstrap boost unit includes an isolation diode D1 and a bootstrap capacitor C1; wherein the cathode of the isolation diode D1 is connected to the positive end of the bootstrap capacitor C1; the anode is connected to the VIN+ terminal as the first input end of the bootstrap boost unit; the other end of the bootstrap capacitor C1 is connected to the output end of the push-pull output unit as the second input end of the bootstrap boost unit.

[0011] Furthermore, the resistance of the oscillation resistor R1 is 10K, the resistance of the threshold resistor R2 and the threshold resistor R3 are 10K, the resistance of the charging resistor R4 is 20K, and the resistance of the positive feedback resistor R5 is 10K.

[0012] Furthermore, the capacitance of the bootstrap capacitor C1 is 1uF, the capacitance of the oscillation capacitor C2 is 10nF, and the capacitance of the filter capacitor C1 is 0.1uF.

[0013] Furthermore, the isolation diode D1 is of model 1N4148WS-7-F.

[0014] Furthermore, the driving transistor Q1 is of model MMBT5401.

[0015] Furthermore, the driving transistor Q2 is of model MMBT5551.

[0016] Furthermore, the comparator U1 is of model TL341DBV.

[0017] Conventional boost circuits, in order to achieve the purpose of converting low voltage to high voltage, often use larger energy storage inductors, which take up a lot of space; at the same time, there are few low-voltage boost chips, which is not easy to make products locally produced, and does not conform to the current market trend of miniaturization, portability, and localization of products. In contrast, the simple pulse-controlled boost circuit provided by the utility model has the following advantages:

[0018] (I) The pulse-controlled boost circuit of the utility model does not use an energy storage inductor, occupies a small space during PCB layout, has a low height, meets the miniaturization standards required by the current market, and has a wide range of applications.

[0019] (II) The pulse-controlled boost circuit of the utility model uses an operational amplifier to build the boost circuit, the circuit is simple, and there are many optional operational amplifier models, which is easy to achieve national production of products. In addition, this circuit has a low frequency and small interference, is more in line with EMI requirements, and has higher reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is the circuit principle diagram of the utility model;

[0021] The reference numerals in the figure represent: 1. Pulse generating unit; 2. Push-pull output unit; 3. Bootstrap boost unit. DETAILED DESCRIPTION

[0022] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of the present application fall within the protection scope of the present invention.

[0023] Embodiment 1:

[0024] The utility model is further described in detail below in conjunction with the accompanying drawings.

[0025] Combination Figure 1 The pulse-controlled boost circuit provided by the utility model comprises a pulse generating unit 1, a push-pull output unit 2 and a bootstrap boost unit 3 which are connected in sequence. Among them:

[0026] The pulse generating unit 1 sets the threshold voltage at the 4th pin of the comparator U1 through the threshold resistors R2 and R3, charges and discharges the oscillation capacitor C2, and generates a comparison voltage at the 3rd pin of the comparator U1. By comparing the threshold voltage and the comparison voltage, the comparator U1 finally outputs a pulse signal composed of high and low levels.

[0027] The push-pull output unit 2 receives the pulse signal output by the pulse generating unit 1 to control the on and off of the driving transistor Q1 and the driving transistor Q2;

[0028] The bootstrap boost unit 3 receives the signal provided by the push-pull output unit 2 and charges the bootstrap capacitor C1, thereby finally increasing the voltage on the bootstrap capacitor.

[0029] In the pulse generating unit 1, the threshold voltage at the 4th pin of the comparator U1 is compared with the comparison voltage at the 3rd pin, and finally the comparator U1 outputs a square wave signal composed of high and low levels.

[0030] In the push-pull output unit 2 , the driving transistor Q1 and the driving transistor Q2 are used to enhance the driving, and the driving transistor Q1 and the driving transistor Q2 can be turned on or off quickly.

[0031] In the bootstrap boost unit 3 , since the isolation diode D1 cannot discharge the bootstrap capacitor C1 in reverse, the voltage of the bootstrap capacitor C1 is the sum of VIN+ and the capacitor charging voltage, thereby increasing the output voltage VOUT.

[0032] Specifically, the selection of each element in this embodiment is as follows:

[0033] The resistance value of the oscillation resistor R1 is 10K, the resistance values ​​of the threshold resistors R2 and R3 are 10K, the resistance value of the charging resistor R4 is 20K, and the resistance value of the positive feedback resistor R5 is 10K.

[0034] The capacitance of the bootstrap capacitor C1 is 1uF, the capacitance of the oscillation capacitor C2 is 10nF, and the capacitance of the filter capacitor C1 is 0.1uF.

[0035] The isolation diode D1 model is 1N4148WS-7-F.

[0036] The driving transistor Q1 model is MMBT5401, and the driving transistor Q2 model is MMBT5551.

[0037] The comparator U1 is TL341DBV.

[0038] The working principle of the utility model is as follows:

[0039] When VIN+ is powered on, assuming that VIN+ is 5V, it is filtered by the filter capacitor C3 in the pulse generating unit 1, and the threshold voltage is set at pin 4 of the comparator U1 through the threshold resistors R2 and R3. The threshold voltage is about 2 / 3 times of VIN+. At the same time, VIN+ charges the oscillation capacitor C2 through the charging resistor R4 and the oscillation resistor R1. Because when VIN+ is powered on, the threshold voltage is established instantly, and the voltage on the oscillation capacitor C2 rises slowly. Therefore, the comparator U1 outputs a high level at the moment of power-on, and the high level is VIN+. When the voltage on the oscillation capacitor C2 is higher than the threshold voltage set at pin 4 of the comparator U1, the comparator U1 outputs a low level, which is 0V. At this time, the threshold voltage at pin 4 of the comparator U1 is approximately 1 / 3 times VIN+. At the same time, the oscillation capacitor C2 is slowly discharged through the oscillation resistor R1. When the voltage on the oscillation capacitor C2 is lower than the threshold voltage set at pin 4 of the comparator U1, the comparator U1 outputs a high level, and the above-mentioned charging and discharging process is repeated again. Finally, the comparator U1 outputs a square wave voltage composed of high and low levels.

[0040] In the push-pull output unit 2, the bases of the driving transistors Q1 and Q2 are connected together and connected in series to the 1st pin of the comparator U1 of the pulse generating unit 1 (i.e., the output end of the pulse generating unit 1), and receive the square wave signal output by the pulse generating unit 1. When the comparator U1 outputs a high level, the base voltage of the driving transistor Q2 is about 5V, and the emitter voltage is about 0V, and the base voltage of the driving transistor Q1 is about 5V, and the emitter voltage is about 4.3V. Since the driving current of the operational amplifier is limited, the collector of the driving transistor Q2 is connected to the VIN+ terminal, which can be used to enhance the drive. Therefore, at this time, the driving transistor Q2 is quickly turned on and the driving transistor Q1 is quickly turned off; when the comparator U1 outputs a low level, similarly, at this time, the driving transistor Q2 is quickly turned off and the driving transistor Q1 is quickly turned on. At this time, the emitter voltage of Q2 is about 0.7V.

[0041] One end of the bootstrap capacitor C1 in the bootstrap boost unit 3 is connected to the emitters of the driving transistor Q1 and the driving transistor Q2. When the driving transistor Q2 is turned on and the driving transistor Q1 is turned off, the voltage at one end of the bootstrap capacitor C1 is about 4.3V; when the driving transistor Q2 is turned off and the driving transistor Q1 is turned on, at this time, the isolation diode D1, the bootstrap capacitor C1, and the driving transistor Q1 form a charging loop to charge the bootstrap capacitor C1. When the next high level comes, since the isolation diode D1 cannot reversely discharge the bootstrap capacitor C1, the voltage of the bootstrap capacitor C1 is the sum of VIN+ and the capacitor charging voltage, thereby achieving an increase in the output voltage VOUT.

[0042] As can be seen from the above, conventional Boost circuits often use larger energy storage inductors to achieve the purpose of converting low voltage to high voltage, which takes up a large space. At the same time, there are few low-voltage Boost chips, which is not easy to localize the product, and does not meet the new market trend of miniaturization, portability, and nationalization of products. In contrast, the simple pulse-controlled boost circuit provided by the utility model does not use energy storage inductors, occupies a small space and has a low height when PCB layout, which meets the miniaturization standards required by the current market. At the same time, the boost circuit is built using an op amp, the circuit is simple, and there are many optional op amp models, which is easy to achieve nationalization of products. In addition, this circuit has a low frequency and low interference, which is more in line with EMI requirements, has higher reliability, and has a wide range of applications.

Claims

1. A pulse-controlled boost circuit, characterized in that: It comprises a pulse generating unit (1), a push-pull output unit (2) and a bootstrap voltage boosting unit (3) which are connected in sequence, wherein: The pulse generating unit (1) comprises an oscillating resistor R1, a threshold resistor R2, a threshold resistor R3, a charging resistor R4, a positive feedback resistor R5, a comparator U1, an oscillating capacitor C2 and a filtering capacitor C3; wherein one end of the threshold resistor R3 is connected to one end of the filtering capacitor C3, pin 5 of the voltage comparator U1 and one end of the charging resistor R4, and the connection point is connected to the VIN+ terminal as the input end of the pulse generating unit (1); the other end of the resistor R3 is connected to one end of the threshold resistor R2, one end of the positive feedback resistor R5 and pin 4 of the voltage comparator U1; the other end of the threshold resistor R2 is connected to one end of the oscillating capacitor C2 and pin 2 of the voltage comparator U1, and the connection point is grounded; the other end of the positive feedback resistor R5 is connected to the other end of the charging resistor R4, one end of the oscillating resistor R1 and the output end of the voltage comparator, and the connection point is connected to the second input end of the push-pull output unit as the output end of the pulse generating unit (1); the other end of the oscillating resistor R1 is connected to pin 3 of the voltage comparator U1 and one end of the oscillating capacitor C2 respectively; The push-pull output unit (2) comprises a driving transistor Q1 and a driving transistor Q2; wherein the collector of the driving transistor Q1 is grounded, and its base is connected to the base of the driving transistor Q2, and the connection point is connected to the output end of the pulse generating unit (1) as the second input end of the push-pull output unit; the emitter of the driving transistor Q1 is connected to the emitter of the driving transistor Q2, and the connection point is connected to the second input end of the bootstrap voltage boosting unit (3) as the output end of the push-pull output unit (2); the collector of the driving transistor Q2 is connected to the VIN+ terminal as the first input end of the push-pull output unit; The bootstrap boost unit (3) comprises an isolation diode D1 and a bootstrap capacitor C1; wherein the cathode of the isolation diode D1 is connected to the positive end of the bootstrap capacitor C1; the anode is connected to the VIN+ terminal as the first input end of the bootstrap boost unit (3); and the other end of the bootstrap capacitor C1 is connected to the output end of the push-pull output unit (2) as the second input end of the bootstrap boost unit (3).

2. The pulse-controlled boost circuit according to claim 1, characterized in that: The resistance value of the oscillation resistor R1 is 10K, the resistance values ​​of the threshold resistors R2 and R3 are 10K, the resistance value of the charging resistor R4 is 20K, and the resistance value of the positive feedback resistor R5 is 10K.

3. The pulse-controlled boost circuit according to claim 1, characterized in that: The capacitance of the bootstrap capacitor C1 is 1uF, the capacitance of the oscillation capacitor C2 is 10nF, and the capacitance of the filter capacitor C1 is 0.1uF.

4. The pulse-controlled boost circuit according to claim 1, characterized in that: The isolation diode D1 is of model 1N4148WS-7-F.

5. The pulse-controlled boost circuit according to claim 1, characterized in that: The driving transistor Q1 is of model MMBT5401.

6. The pulse-controlled boost circuit according to claim 1, characterized in that: The driving transistor Q2 is of model MMBT5551.

7. The pulse-controlled boost circuit according to claim 1, characterized in that: The comparator U1 is of model TL341DBV.

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