Synchronous step-down circuit of single-chip microcomputer

Abstract

The utility model discloses a synchronous step-down circuit of a single-chip microcomputer, which relates to the field of voltage conversion and comprises a single-chip microcomputer power supply module used for supplying power to the single-chip microcomputer; the half-bridge power supply module is used for supplying power to the half-bridge driving voltage reduction module; the current sampling module is used for sampling a flowing current of an electricity load, converting the flowing current into a voltage signal, amplifying the voltage signal and outputting the amplified voltage signal to the single-chip microcomputer; compared with the prior art, the utility model has the beneficial effects that the circuit adopts synchronous rectification, depends on an MOS (Metal Oxide Semiconductor) tube in a follow current stage, selects an MOS with low internal resistance, and has lower voltage drop which is about 0.02 V, so that compared with an asynchronous voltage reduction circuit in the prior art, the circuit has huge comparative advantages; a single-chip microcomputer and a half-bridge drive (a half-bridge drive voltage reduction module) are adopted, so that the driving capability is higher, and the efficiency is higher; a high-precision operational amplifier (a current sampling module) is adopted, and the adopted voltage can be designed to be 0.01 V or even lower, so that the efficiency is high, and the size is small.

Description

Technical Field

[0001] This utility model relates to the field of voltage conversion, specifically a microcontroller synchronous step-down circuit. Background Technology

[0002] Please see Figure 1 This is a standard asynchronous buck converter circuit. Chip U1 is the asynchronous buck controller, capacitors C1 and C2 are input filter capacitors, and SMBJ28A is a TVS diode used to suppress instantaneous power-on pulse protection. Pin 1 of chip U1 is the input terminal, and pin 2 is used to detect the voltage difference of the parallel network of resistors R1 and R2 to control the output current. Pin 3 of U1 is the dimming pin. The voltage divider of resistors R5 and R4 is filtered by capacitor C5 to power chip U2. Chip U2 outputs a high voltage when the supply voltage is higher than 2.5V and a low voltage when it is lower than 2.5V. The output is filtered by resistor R3 and capacitor C4 before reaching the dimming pin, achieving the function of low input voltage protection. Pin 5 of chip U1 drives MOSFET Q1, controlling the output current by controlling the PWM duty cycle. Pin 6 of chip U1 is the internal LDO output pin, connected to capacitor C3 to filter the internal LDO output. L1 is a voltage-to-current conversion inductor. Diodes D3, D4, and D5 are diodes that carry the current of the freewheeling inductor when the switching transistor is off. Chip U1 adjusts its duty cycle based on the detected voltage difference across resistors R1 and R2, keeping the voltage difference at 0.2V, thus achieving a constant current effect.

[0003] Because of the low efficiency of asynchronous step-down characteristics, the freewheeling stage uses a diode for freewheeling. The diode is characterized by a large voltage drop, usually 0.4-0.5V. If the current is 20A, the power loss is 0.4*20=8W, which is inefficient and causes excessive heat generation, and needs to be improved. Utility Model Content

[0004] The purpose of this invention is to provide a single-chip microcomputer synchronous step-down circuit to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, this utility model provides the following technical solution:

[0006] A microcontroller synchronous step-down circuit includes:

[0007] The microcontroller power supply module is used to generate 5V voltage to power the microcontroller.

[0008] The half-bridge power supply module is used to generate 9V voltage to power the half-bridge drive buck module;

[0009] The current sampling module is used to sample the current flowing through the electrical load, convert it into a voltage signal, amplify it, and output it to the microcontroller.

[0010] The half-bridge driver buck module is used to receive control from the microcontroller and synchronously buck the voltage by controlling whether the two MOSFETs are turned on or off, so as to output voltage to drive the load to work.

[0011] A microcontroller is used for the operation of integrated control circuits;

[0012] The microcontroller power supply module is connected to the microcontroller, the half-bridge power supply module is connected to the half-bridge driver step-down module, the current sampling module is connected to the microcontroller, and the microcontroller is connected to the half-bridge driver step-down module.

[0013] As a further improvement of this utility model: the microcontroller is model SN32F805J, pin 3 of the microcontroller is connected to the current sampling module, pin 24 of the microcontroller is connected to the microcontroller power supply module through resistor R4, and pins 12 and 13 of the microcontroller are connected to the half-bridge drive buck module.

[0014] As a further improvement of this utility model: the microcontroller power supply module includes chip U2, the model of chip U2 is SGM2230, pin 3 of chip U2 is connected to power supply BAT+ through resistor R6, pin 1 of chip U2 is grounded, pin 2 of chip U2 is connected to the microcontroller and one end of capacitor C2, and the other end of capacitor C2 is grounded.

[0015] As a further improvement of this utility model: the half-bridge power supply module includes a chip U1, the model of which is SGM61410. Pin 5 of chip U1 is connected to the power supply BAT+ through resistor R2. Pin 4 of chip U1 is connected to the microcontroller through resistor R1. Pin 3 of chip U1 is connected to one end of resistor R3 and one end of resistor R5. The other end of resistor R3 is connected to one end of capacitor C4, one end of inductor L1, and the half-bridge drive buck module. The other end of resistor R5 is grounded, the other end of capacitor C4 is grounded, the other end of inductor L1 is connected to pin 1 of chip U1 through capacitor C3, and the other end of inductor L1 is directly connected to pin 6 of chip U1.

[0016] As a further improvement of this utility model: the current sampling module includes a chip U4, the model of which is LTC8381. Pin 3 of chip U4 is connected to one end of resistor R20, one end of resistor R21, and the negative terminal L- of the load. The other end of resistor R20 is grounded, and the other end of resistor R21 is grounded. Pin 4 of chip U4 is connected to one end of resistor R16 and one end of resistor R18. The other end of resistor R18 is grounded. The other end of resistor R16 is connected to one end of capacitor C17, pin 1 of chip U4, and the microcontroller. The other end of capacitor C17 is grounded. Pin 2 of chip U4 is grounded, and pin 5 of chip U4 is connected to the microcontroller.

[0017] As a further improvement of this utility model: the half-bridge drive buck module includes chip U5, MOSFET Q2, and MOSFET Q3. The model of chip U5 is SQ55664. Pin 1 of chip U5 is connected to the half-bridge power supply module through resistor R17. Pins 5 and 6 of chip U5 are connected to the microcontroller. Pin 3 of chip U5 is connected to the first terminal of MOSFET Q2. Pin 8 of chip U5 is connected to the first terminal of MOSFET Q3. Pin 2 of chip U5 is connected to pin 4 of chip U5, the second terminal of MOSFET Q2, the third terminal of MOSFET Q3, and one end of inductor L2 through capacitor C19. The second terminal of MOSFET Q3 is grounded. The third terminal of MOSFET Q2 is connected to the power supply BAT+, the negative terminal of TVS diode D3, and one end of the first capacitor bank. The positive terminal of TVS diode D3 is grounded. The other end of the first capacitor bank is grounded. The other end of inductor L2 is connected to one end of the second capacitor bank and the positive terminal L+ of the load. The other end of the second capacitor bank is grounded. The capacitor bank is composed of multiple capacitors connected in parallel.

[0018] Compared with the prior art, the beneficial effects of this utility model are as follows: The circuit of this utility model is a synchronous rectification circuit, and the freewheeling stage relies on a MOSFET. A low internal resistance MOSFET is selected, resulting in a small voltage drop of about 0.02V, which is a huge advantage compared with the asynchronous buck circuit of the prior art; a single-chip microcomputer plus half-bridge driver (half-bridge driver buck module) is adopted, which has stronger driving capability and higher efficiency; a high-precision operational amplifier (current sampling module) is used, and the voltage can be designed down to 0.01V or even lower, which results in high efficiency and small size. Attached Figure Description

[0019] Figure 1 This is a circuit diagram of an existing asynchronous buck converter circuit.

[0020] Figure 2 This is a circuit diagram of a microcontroller synchronous step-down circuit. Detailed Implementation

[0021] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the protection scope of the present utility model.

[0022] Please see Figure 2 A single-chip microcomputer synchronous step-down circuit includes:

[0023] The microcontroller power supply module is used to generate 5V voltage to power the microcontroller.

[0024] The half-bridge power supply module is used to generate 9V voltage to power the half-bridge drive buck module;

[0025] The current sampling module is used to sample the current flowing through the electrical load, convert it into a voltage signal, amplify it, and output it to the microcontroller.

[0026] The half-bridge driver buck module is used to receive control from the microcontroller and synchronously buck the voltage by controlling whether the two MOSFETs are turned on or off, so as to output voltage to drive the load to work.

[0027] A microcontroller is used for the operation of integrated control circuits;

[0028] The microcontroller power supply module is connected to the microcontroller, the half-bridge power supply module is connected to the half-bridge driver step-down module, the current sampling module is connected to the microcontroller, and the microcontroller is connected to the half-bridge driver step-down module.

[0029] In this embodiment: Please refer to Figure 2 The microcontroller is model SN32F805J. Pin 3 of the microcontroller is connected to the current sampling module, pin 24 of the microcontroller is connected to the microcontroller power supply module through resistor R4, and pins 12 and 13 of the microcontroller are connected to the half-bridge driver buck module.

[0030] When the circuit is operating, pin 4 of the microcontroller (labeled U3 in the attached diagram) activates pin 4 of the buck converter U1, enabling U1 to power the half-bridge converter U5. Pin 3 of the microcontroller reads the sampled voltage amplified by the amplifier U4. Based on the voltage read from pin 3, the microcontroller adjusts the output duty cycle to regulate the output current (a common technique, not innovative), achieving constant current. The microcontroller also reads the input voltage sampling networks R11, R13, and C7, using the battery voltage type to limit the maximum output duty cycle. Furthermore, the microcontroller reads the temperature sampling networks R15, R14, and C8, adjusting the voltage level according to the temperature to limit the operating temperature.

[0031] In this embodiment: Please refer to Figure 2 The microcontroller power supply module includes chip U2, model SGM2230. Pin 3 of chip U2 is connected to power supply BAT+ through resistor R6. Pin 1 of chip U2 is grounded. Pin 2 of chip U2 is connected to the microcontroller and one end of capacitor C2. The other end of capacitor C2 is grounded.

[0032] The power supply BAT+ supplies power to chip U2 through an RC network composed of resistors R6, R7, and capacitor C5. Resistor R6 also serves to share power with chip U2. The output voltage of chip U2 is filtered by capacitor C2, and then filtered again by resistor R4 and capacitor C9 to supply power to microcontroller U3.

[0033] In this embodiment: Please refer to Figure 2The half-bridge power supply module includes chip U1, model SGM61410. Pin 5 of chip U1 is connected to the power supply BAT+ through resistor R2. Pin 4 of chip U1 is connected to the microcontroller through resistor R1. Pin 3 of chip U1 is connected to one end of resistor R3 and one end of resistor R5. The other end of resistor R3 is connected to one end of capacitor C4, one end of inductor L1, and the half-bridge driver buck module. The other end of resistor R5 is grounded, the other end of capacitor C4 is grounded, the other end of inductor L1 is connected to pin 1 of chip U1 through capacitor C3, and the other end of inductor L1 is directly connected to pin 6 of chip U1.

[0034] Power supply BAT+ supplies power to chip U1 via an RC network composed of R2 and C1. This RC network suppresses voltage spikes, protecting chip U1. The voltage divider network resistors R3 and R5 are connected to pin 3 of chip U1, which is the voltage feedback pin used to set the output voltage. Capacitor C4 is the output filter capacitor. Inductor L1 is the voltage conversion inductor. Capacitor C3 is the bootstrap capacitor of chip U1, used to power the internal switching control circuit of chip U1. Pin 4 of chip U1 connects to the microcontroller through resistor R1. The current-limiting effect of resistor R1 allows the microcontroller to safely control the switching on and off of chip U1.

[0035] In this embodiment: Please refer to Figure 2 The current sampling module includes chip U4, model LTC8381. Pin 3 of chip U4 is connected to one end of resistor R20, one end of resistor R21, and the negative terminal L- of the load. The other end of resistor R20 and the other end of resistor R21 are grounded. Pin 4 of chip U4 is connected to one end of resistor R16 and one end of resistor R18. The other end of resistor R18 is grounded. The other end of resistor R16 is connected to one end of capacitor C17, pin 1 of chip U4, and the microcontroller. The other end of capacitor C17 is grounded. Pin 2 of chip U4 is grounded. Pin 5 of chip U4 is connected to the microcontroller.

[0036] The current sampling module is an operational amplifier circuit with non-inverting ratio. The operational amplifier chip U4 collects the current flowing through resistors R20 and R21, that is, the current supplied to ground by resistors R20 and R21 by the negative terminal of the load. After being amplified by the voltage divider network of resistors R16 and R18, the amplified voltage signal is output from pin 1 of chip U4, filtered by capacitor C17, and then transmitted to the AD sampling pin of the microcontroller for sampling.

[0037] In this embodiment: Please refer to Figure 2The half-bridge driver buck module includes chip U5, MOSFET Q2, and MOSFET Q3. Chip U5 is model SQ55664. Pin 1 of chip U5 is connected to the half-bridge power supply module through resistor R17. Pins 5 and 6 of chip U5 are connected to the microcontroller. Pin 3 of chip U5 is connected to the first terminal of MOSFET Q2. Pin 8 of chip U5 is connected to the first terminal of MOSFET Q3. Pin 2 of chip U5 is connected to pin 4 of chip U5, the second terminal of MOSFET Q2, the third terminal of MOSFET Q3, and one end of inductor L2 through capacitor C19. The second terminal of MOSFET Q3 is grounded. The third terminal of MOSFET Q2 is connected to the power supply BAT+, the negative terminal of TVS diode D3, and one end of the first capacitor bank. The positive terminal of TVS diode D3 is grounded. The other end of the first capacitor bank is grounded. The other end of inductor L2 is connected to one end of the second capacitor bank and the positive terminal L+ of the load. The other end of the second capacitor bank is grounded. The capacitor bank consists of multiple capacitors connected in parallel.

[0038] The first capacitor bank consists of six capacitors connected in parallel: C10, C11, C13, C14, C16, and C18 are input filter capacitors. TVS diode D3 is used to suppress voltage spikes during power-on for protection. MOSFET Q2 is the upper-switching MOSFET controlling the input current. MOSFET Q3 is the lower-switching synchronous rectifier MOSFET. Inductor L2 is the main power inductor used for efficient voltage and current conversion. The second capacitor bank consists of four capacitors connected in parallel: C20, C21, C22, and C23 are output filter capacitors. Capacitor C19 is a bootstrap capacitor used to power the circuit driving the upper-switching MOSFET. Pin 5 of chip U2 receives the signal controlling the upper-switching MOSFET, and pin 6 receives the signal controlling the lower-switching MOSFET.

[0039] For a comprehensive comparison, please refer to [link / reference]. Figure 1 and Figure 2 ,

[0040] 1. Existing technology cannot handle high currents, such as those required for high-power lighting. The driving capability of dedicated chips on the market is relatively weak. When driving high-power MOSFETs, the large parasitic capacitance of the MOSFETs requires a larger driving current, which can distort the driving waveform, leading to excessive heat generation, low efficiency, or even burnout of the MOSFET.

[0041] This invention uses an MCU plus a half-bridge driver, which provides stronger driving capability and higher efficiency.

[0042] 2. Existing technologies suffer from low efficiency due to their asynchronous step-down characteristics. During the freewheeling phase, a diode is used for freewheeling. Diodes are characterized by a large voltage drop, typically 0.4-0.5V. If the current is 20A, the power loss is 0.4 * 20 = 8W, resulting in overheating. This leads to low efficiency and significant heat generation.

[0043] This invention is a synchronous rectification, with the freewheeling stage relying on a MOSFET. A low internal resistance MOSFET is selected, resulting in a small voltage drop of approximately 0.02V, which is a significant advantage.

[0044] 3. Existing technology has low accuracy, with a sampling voltage of 0.2V. Because of the low accuracy, large-value resistors must be selected, which causes excessive heat generation under high current, resulting in low efficiency. At the same time, the use of high-power resistors also occupies more space.

[0045] In this invention, we use a high-precision operational amplifier with a voltage that can be designed down to 0.01V or even lower, resulting in high efficiency and small size.

[0046] In summary, compared with the prior art, this utility model has higher efficiency, higher reliability, less heat generation, and a wider range of applicable power.

[0047] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects.

[0048] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A microcontroller synchronous step-down circuit, characterized in that, The microcontroller synchronous buck circuit includes: The microcontroller power supply module is used to supply power to the microcontroller. The half-bridge power supply module is used to supply power to the half-bridge drive buck module; The current sampling module is used to sample the current flowing through the electrical load, convert it into a voltage signal, amplify it, and output it to the microcontroller. The half-bridge driver buck module is used to receive control from the microcontroller and synchronously buck the voltage by controlling whether the two MOSFETs are turned on or off, so as to output voltage to drive the load to work. A microcontroller is used for the operation of integrated control circuits; The microcontroller power supply module is connected to the microcontroller, the half-bridge power supply module is connected to the half-bridge driver step-down module, the current sampling module is connected to the microcontroller, and the microcontroller is connected to the half-bridge driver step-down module.

2. The monolithic microcomputer synchronous step-down circuit according to claim 1, characterized by The microcontroller is model SN32F805J. Pin 3 of the microcontroller is connected to the current sampling module, pin 24 of the microcontroller is connected to the microcontroller power supply module through resistor R4, and pins 12 and 13 of the microcontroller are connected to the half-bridge driver buck module.

3. The microcontroller synchronous step-down circuit according to claim 2, characterized in that, The microcontroller power supply module includes chip U2, model SGM2230. Pin 3 of chip U2 is connected to the power supply BAT+ through resistor R6. Pin 1 of chip U2 is grounded. Pin 2 of chip U2 is connected to the microcontroller and one end of capacitor C2. The other end of capacitor C2 is grounded.

4. The microcontroller synchronous step-down circuit according to claim 1, characterized in that, The half-bridge power supply module includes chip U1, model SGM61410. Pin 5 of chip U1 is connected to the power supply BAT+ via resistor R2. Pin 4 of chip U1 is connected to the microcontroller via resistor R1. Pin 3 of chip U1 is connected to one end of resistor R3 and one end of resistor R5. The other end of resistor R3 is connected to one end of capacitor C4, one end of inductor L1, and the half-bridge driver buck module. The other end of resistor R5 is grounded, the other end of capacitor C4 is grounded, the other end of inductor L1 is connected to pin 1 of chip U1 via capacitor C3, and the other end of inductor L1 is directly connected to pin 6 of chip U1.

5. The microcontroller synchronous step-down circuit according to claim 1, characterized in that, The current sampling module includes chip U4, model LTC8381. Pin 3 of chip U4 is connected to one end of resistor R20, one end of resistor R21, and the negative terminal L- of the load. The other end of resistor R20 and the other end of resistor R21 are grounded. Pin 4 of chip U4 is connected to one end of resistor R16 and one end of resistor R18. The other end of resistor R18 is grounded. The other end of resistor R16 is connected to one end of capacitor C17, pin 1 of chip U4, and the microcontroller. The other end of capacitor C17 is grounded. Pin 2 of chip U4 is grounded. Pin 5 of chip U4 is connected to the microcontroller.

6. The microcontroller synchronous buck circuit according to any one of claims 1 to 5, characterized in that, The half-bridge driver buck module includes chip U5, MOSFET Q2, and MOSFET Q3. Chip U5 is model SQ55664. Pin 1 of chip U5 is connected to the half-bridge power supply module through resistor R17. Pins 5 and 6 of chip U5 are connected to the microcontroller. Pin 3 of chip U5 is connected to the first terminal of MOSFET Q2. Pin 8 of chip U5 is connected to the first terminal of MOSFET Q3. Pin 2 of chip U5 is connected to pin 4 of chip U5, the second terminal of MOSFET Q2, the third terminal of MOSFET Q3, and one end of inductor L2 through capacitor C19. The second terminal of MOSFET Q3 is grounded. The third terminal of MOSFET Q2 is connected to the power supply BAT+, the negative terminal of TVS diode D3, and one end of the first capacitor bank. The positive terminal of TVS diode D3 is grounded. The other end of the first capacitor bank is grounded. The other end of inductor L2 is connected to one end of the second capacitor bank and the positive terminal L+ of the load. The other end of the second capacitor bank is grounded. The capacitor bank consists of multiple capacitors connected in parallel.

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