PWM waveform generation circuit for DC-DC conversion

Abstract

The utility model discloses a PWM waveform generation circuit for DC-DC conversion. The PWM waveform generation circuit comprises a single-chip microcomputer circuit (11) and an AND operation circuit (12). The system is characterized in that a first output end of the single-chip microcomputer circuit (11) is configured to output a waveform PWM1, a second output end of the single-chip microcomputer circuit (11) is configured to output a waveform PWM2, a third output end of the single-chip microcomputer circuit (11) is configured to output a waveform PWM3, the waveform PWM1 and the waveform PWM2 are a pair of pulse waveforms which are the same in frequency, opposite in phase and adjustable in duty ratio, the waveform PWM3 and the waveform PWM2 are the same in frequency and different in phase conversion time, and the waveform PWM1 and the waveform PWM2 are different in phase conversion time. The duty ratio of the waveform PWM3 is adjustable; the second output end and the third output end of the single-chip microcomputer circuit (11) are electrically connected with the two input ends of the AND operation circuit (12) respectively, and the output end of the AND operation circuit (12) is electrically connected with the PWML input end of the switching tube driving circuit (2). And a single-chip microcomputer chip with low cost is used.

Description

Technical Field

[0001] The utility model relates to the technical field of direct current switching power supplies, in particular to a PWM waveform generating circuit for DC-DC conversion. Background Art

[0002] DC-DC converters are widely used in power electronic equipment. In order to improve the reliability and conversion efficiency of the converter, it is necessary to control and optimize the dead time between the upper and lower arm switches of the DC-DC converter.

[0003] The DC-DC converter includes a BUCK circuit for stepping down the voltage or a BOOST circuit for stepping up the voltage, wherein the BUCK circuit is divided into an asynchronous BUCK circuit and a synchronous BUCK circuit, and the BOOST circuit is divided into an asynchronous BOOST circuit and a synchronous BOOST circuit.

[0004] The synchronous BUCK circuit consists of upper and lower bridge arm switch tubes, energy storage inductors, and output filter capacitors. When the circuit is working, the PWM signal controls the two MOS tubes to conduct alternately, thereby controlling the charging and discharging of the inductor. The difference from the asynchronous BUCK circuit architecture is that the synchronous BUCK circuit uses MOS switches to participate in freewheeling to obtain lower freewheeling power consumption than the freewheeling diode.

[0005] In the synchronous BUCK circuit, PWMH is used to represent the driving waveform of the upper bridge arm MOS Q1, and PWML is used to represent the driving waveform of the lower bridge arm MOS Q2; I L Represents the inductor current waveform, then, there is a short period of time on the PWMH and PWML waveforms. In this time interval, PWMH and PWML are both low. This time interval is the dead time. When PWMH is high and PWML is low, the upper arm tube MOS Q1 is turned on, the lower arm tube Q2 is turned off, and the inductor current rises; when PWMH is low and PWML is high, the upper arm tube MOS Q1 is turned off, the lower arm tube Q2 is turned on, and the inductor realizes freewheeling through Q2.

[0006] The existence of dead time in the BUCK circuit is because the so-called synchronization is relative. The control of the upper and lower bridge arm switches cannot be completely seamless, with one open and the other closed. Therefore, the controller follows a principle: it is better to close the upper and lower bridge arm switches at the same time to prevent the current from passing, rather than to allow the upper and lower bridge arm switches to have a chance to open at the same time, so that the current directly short-circuits from the power input end through the upper and lower bridge arm switches to the power ground. Therefore, there must be a certain dead time between the drive signals of the upper and lower bridge arm switches to prevent the power input end from short-circuiting with the power ground through the upper and lower bridge arm switches, that is, during the dead time, the upper and lower bridge arm switches are not turned on. Any controller needs to avoid the upper and lower bridge arm switches being turned on at the same time. If this state occurs, it is very easy to cause damage to the upper and lower bridge arm switches, because it is equivalent to short-circuiting the input power supply and GND through the upper and lower bridge arm switches. In order to avoid this state, it is necessary to wait for a period of time after the upper bridge arm switch Q1 is turned off before turning on the lower bridge arm switch. The state in which both the upper and lower bridge arm switches are turned off is called dead time. During the dead time, the parasitic diode of the lower bridge arm switch or the external diode connected in parallel with the lower bridge arm switch is mainly used for freewheeling.

[0007] During the dead time, the freewheeling power consumption of the switch tube is the power consumption of the parasitic diode of the lower bridge arm switch tube, that is, the forward conduction voltage drop of the diode multiplied by the freewheeling current at this time.

[0008] In the synchronous BOOST circuit, the diode D is replaced by the MOS tube Q2. When Q1 is turned on, Q2 is turned off, and when Q1 is turned off, Q2 is turned on. Q2 replaces the function of the diode. Since Q1 and Q2 can be in saturation conduction when they are turned on, the power consumption of Q2 tube will be greatly reduced, and the overall efficiency is improved. Such a synchronous on-off circuit is called a synchronous BOOST circuit. In the actual circuit, due to the inconsistency of the time delay between the MOS tubes Q1 and Q2 and the influence of the distributed capacitance and inductance of the circuit itself, when Q1 is turned on, Q2 cannot be turned off at the same time. Conversely, when Q2 is turned on, Q1 cannot be really turned off at the same time, but there is a time difference. This time difference will generate a large current and power consumption in the Q1 and Q2 loops, and will cause damage to the MOS tubes Q1 and Q2. Therefore, the dead time must also be set in the synchronous BOOST circuit.

[0009] The application number is CN202210649514.4, and the name of the invention is "A method for setting the intermittent working dead zone of SiC MOSFET Boost converter in synchronous working mode". A method for setting the intermittent working dead zone of a converter is provided, including: obtaining the actual duty cycle D, the input side voltage Vi and the output side voltage Vo of the converter, and setting the dead time before the main switch tube M1 is turned on to Tahead; obtaining relevant parameter information of the SiC MOSFET device and its driving circuit, and setting the dead time after the main switch tube M1 is turned off to Tafter. The above steps are completed within n switching cycles, and the method is executed with n cycles as a cycle time. The dead zone setting method of the present invention takes into account not only the situation that the converter works in the intermittent mode, but also the capacitive loss of SiCMOSFET and the freewheeling loss of the diode, thereby improving the efficiency of the converter in the intermittent working mode without the need for additional hardware circuits.

[0010] The patent with application number CN201811301863.7 and invention name "A dead zone setting method and its application device" provides a method for controlling the switch tube used for power output in the inverter to delay the first time to turn on and delay the second time to turn off, so as to maximize the on-time of the switch tube, improve the quality of the circuit output current, and effectively reduce harmonic distortion; at the same time, by controlling the other switch tube of complementary drive to turn off normally and delay the third time to turn on, and the third time is longer than the second time, to ensure that there is a dead zone for the complementary control signals of the two switch tubes to avoid direct conduction. In addition, when the power factor of the circuit where the two switch tubes are located changes, this method will obtain different judgment results according to the different power factors, and further set the corresponding time lengths of the two switch tubes delayed on and off under the current power factor, avoiding the problem of weakening the dead zone compensation effect due to different power factors in the prior art. This patent sets a dead time Td between the control signals of the two switching devices in the upper and lower bridge arms of the same phase; the original control signal D1 / D11 is changed to D1' / D11', so that the turned-on power device can be reliably turned off, and after a certain period of time, the turned-off power device is triggered again. During this period of time, the power devices in the upper and lower bridge arms are in the turned-off state.

[0011] The patent with application number CN202211149632.5 and invention name "A driving circuit for a high-efficiency Buck converter" provides a driving circuit including: a pass-through protection circuit, a high-side circuit and a low-side circuit; the pass-through protection circuit is connected to the high-side circuit and the low-side circuit respectively; the pass-through protection circuit is used to prevent circuit damage; the high-side circuit is used to receive the PWM signal transmitted by the pass-through protection circuit, and generate a dynamic dead time from the high side to the low side; the low-side circuit is used to receive the PWM signal transmitted by the pass-through protection circuit, and generate a dead time from the low side to the high side. This application combines the application scenario of a wide input voltage range, uses the inductor current to change the charging and discharging time of the SW node capacitor, and then realizes the dynamic adjustment of the dead time under different load current conditions, ensuring the reliability of DC-DC while reducing power loss and improving efficiency; at the same time, the narrow pulse generation circuit part is omitted to further reduce static power consumption and improve system efficiency.

[0012] In the prior art, although different methods are provided for optimizing the dead time setting, and the corresponding switch tube control waveform PWM generation methods are provided, the existing switch tube control waveform PWM generation circuit cannot be implemented using a single-chip microcomputer chip with simplified functions and low price, which limits the further reduction of the manufacturing cost of the DC-DC converter. Summary of the invention

[0013] The utility model aims to provide a PWM waveform generating circuit for DC-DC conversion constructed by using a single-chip microcomputer chip with simplified functions and low price, which can further reduce the manufacturing cost of the DC-DC converter.

[0014] To achieve this purpose, the utility model adopts the following technical solutions:

[0015] A DC-DC converter PWM waveform generating circuit comprises a single chip computer circuit (11) and an AND operation circuit (12); the characteristics are:

[0016] The first output end of the single-chip circuit (11) is configured to output waveform PWM1, the second output end is configured to output waveform PWM2, and the third output end is configured to output waveform PWM3, wherein waveform PWM1 and waveform PWM2 are a pair of pulse waveforms with the same frequency and opposite phases and adjustable duty cycle, waveform PWM3 and waveform PWM2 have the same frequency and different phase conversion time, and the duty cycle of waveform PWM3 is adjustable;

[0017] The first output terminal of the single-chip circuit (11) is electrically connected to the PWMH input terminal of the switch tube drive circuit (2), and the waveform PWM1 is converted into the switch tube drive waveform HO after being converted by the switch tube drive circuit (2);

[0018] The second and third output ends of the single-chip circuit (11) are electrically connected to the two input ends of the AND operation circuit (12), respectively; the output end of the AND operation circuit (12) is electrically connected to the PWML input end of the switch tube drive circuit (2); the AND operation circuit (12) performs an AND operation on the waveform PWM2 and the waveform PWM3 to generate a waveform PWML, and the waveform PWML is converted into a switch tube drive waveform LO after being converted by the switch tube drive circuit (2).

[0019] The beneficial effects of the utility model are:

[0020] The PWM waveform generating circuit for a DC-DC converter provided by the utility model uses a single-chip microcomputer chip with simplified functions and low price to construct the PWM waveform generating circuit for DC-DC conversion, thereby further reducing the manufacturing cost of the DC-DC converter.

[0021] Other features and advantages of the present invention will be described in the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of a PWM waveform generating circuit composition given in a specific implementation mode of the utility model;

[0023] Figure 2 It is a schematic diagram of a PWM waveform generating circuit structure given in a specific implementation mode of the utility model;

[0024] Figure 3 It is a waveform diagram of a PWM waveform generating circuit given in a specific implementation mode of the utility model;

[0025] Figure 4 It is a schematic diagram of a PWM waveform generating circuit for a BUCK circuit given in a specific embodiment of the utility model;

[0026] Figure 5 The utility model provides a PWM waveform generating circuit for a BOOST circuit schematic diagram according to a specific implementation manner.

[0027] In the figure, 1. PWM waveform generation circuit; 11. Single chip microcomputer circuit; 12. “AND” operation circuit; 2. Switch tube driving circuit; 3. Detection circuit. DETAILED DESCRIPTION

[0028] The technical solution of the utility model is further explained below with reference to the accompanying drawings and through specific implementation methods.

[0029] The utility model provides a PWM waveform generating circuit for DC-DC conversion which is constructed by using a single-chip microcomputer chip with simplified functions and low price, and can further reduce the manufacturing cost of the DC-DC converter.

[0030] The utility model provides a PWM waveform generating circuit for DC-DC conversion, comprising a single chip computer circuit (11) and an AND operation circuit (12); the characteristics are:

[0031] The first output end of the single-chip circuit (11) is configured to output waveform PWM1, the second output end is configured to output waveform PWM2, and the third output end is configured to output waveform PWM3, wherein waveform PWM1 and waveform PWM2 are a pair of pulse waveforms with the same frequency and opposite phases and adjustable duty cycle, waveform PWM3 and waveform PWM2 have the same frequency and different phase conversion time, and the duty cycle of waveform PWM3 is adjustable;

[0032] The first output terminal of the single-chip circuit (11) is electrically connected to the PWMH input terminal of the switch tube drive circuit (2), and the waveform PWM1 is converted into the switch tube drive waveform HO after being converted by the switch tube drive circuit (2);

[0033] The second and third output ends of the single-chip circuit (11) are electrically connected to the two input ends of the AND operation circuit (12), respectively; the output end of the AND operation circuit (12) is electrically connected to the PWML input end of the switch tube drive circuit (2); the AND operation circuit (12) performs an AND operation on the waveform PWM2 and the waveform PWM3 to generate a waveform PWML, and the waveform PWML is converted into a switch tube drive waveform LO after being converted by the switch tube drive circuit (2).

[0034] Specifically, see Figure 1 As shown, the first and second output terminals of the single-chip microcomputer circuit (11) are output terminals of a digital pulse waveform generating circuit in the single-chip microcomputer chip, whose period and duty cycle can be configured by an internal digital processing unit; the third output terminal of the single-chip microcomputer circuit (11) is an output terminal of a digital pulse waveform generating circuit in the single-chip microcomputer chip, whose period and duty cycle can be configured by an internal digital processing unit, and the waveform PWM3 outputted from the third output terminal has a different phase conversion time from the waveform PWM1 outputted from the first output terminal, and there is a definite time correspondence relationship between the phase conversion time of the waveform PWM1 and the waveform PWM3.

[0035] Specifically, a specific model of the single-chip microcomputer circuit (11) is TLSR8359, which is produced by a Chinese enterprise.

[0036] Specifically, a specific model of the switch tube driving circuit (2) is NSD1224, which is produced by a Chinese enterprise.

[0037] The switch tube driving circuit (2) is used to convert the waveform PWMH from the first output end of the single chip circuit (11) and the waveform PWML from the output end of the AND operation circuit (12) into switch tube driving signals HO and LO respectively. The voltage and current characteristics of HO and LO meet the requirements for driving the switch tube action.

[0038] Specifically, the phase switching time between the pulse waveform PWM1 with adjustable duty cycle and the pulse waveform PWM3 with adjustable duty cycle is different, and there is a certain time correspondence between the phase switching time of the waveform PWM1 and the waveform PWM3, and this time correspondence includes:

[0039] There is a dead time T between the pulse waveform PWM1 with adjustable duty cycle and the pulse waveform PWM3 with adjustable duty cycle, in which both are at low level. d1 and T d2 , see Figure 3 As shown, the dead time T d1 and T d2 Determines the dead time between PWMH and PWML; and,

[0040] During the dead time T d1 and T d2 In addition, the high and low levels of the duty cycle adjustable pulse waveform PWM1 and the duty cycle adjustable pulse waveform PWM3 are in opposite phases to each other; and,

[0041] The cycle time of the pulse waveform PWM1 with adjustable duty cycle is the same as the cycle time of the pulse waveform PWM3 with adjustable duty cycle.

[0042] Specifically, the high level of the pulse waveform PWML with adjustable duty cycle is used to drive the lower bridge arm switch tube Q2 for the energy storage inductor to enter the on state. A specific implementation method is: using the pulse waveform PWML with adjustable duty cycle to send a high level pulse to the control end of the lower bridge arm switch tube Q2 for the energy storage inductor to continue the current, and the rising edge of the high level pulse lags behind the falling edge of the pulse waveform PWMH in the same period by a first dead time T d1 The falling edge of the high-level pulse precedes the rising edge of the pulse waveform PWMH of the next cycle by a second dead time T d2 .

[0043] Typically, the time width T of the high-level pulse sent by the pulse waveform PWML with adjustable duty cycle to the control end of the lower bridge arm switch tube Q2 for the energy storage inductor is ON , the low level duration of the pulse waveform PWMH with adjustable duty cycle and the first dead time T d1 , Second dead time T d2 OK, see Figure 3 Shown: TON = T con -T d1 -T △ ; Among them, T ON is the time length of the lower bridge arm switch tube Q2 actually participating in the freewheeling, T con Is to use V in 、V out , T inj And the relationship (V in -V out ) / V out = T con / T inj The solved freewheeling time, T △ It is T con The time correction amount; the T con The value is reduced by a time correction amount T △ The latter is used as the actual conduction time of the lower bridge arm switch tube Q2 to ensure that the actual conduction time of the lower bridge arm switch tube Q2 is less than or equal to the actual freewheeling time required by the energy storage inductor L1. out is the measured value of the voltage at the output of the energy storage inductor L1 of the BUCK circuit, V in V is the voltage at the input of the energy storage inductor L1 of the BUCK circuit in The measured value.

[0044] Typically, when the duty cycle of the duty-cycle adjustable pulse waveform PWMH used to drive the upper bridge arm switch tube does not change, the time width of the high-level pulse sent by the duty-cycle adjustable pulse waveform PWML to the control end of the lower bridge arm switch tube Q2 for the energy storage inductor to continue current also remains unchanged.

[0045] The utility model provides a PWM waveform generating circuit for DC-DC conversion, which is characterized by:

[0046] The single-chip computer circuit (11) comprises a PWM waveform parameter determination circuit, the PWM waveform parameter determination circuit comprises a digital operation circuit, a storage circuit and a PWM waveform oscillation circuit, the operation circuit performs a PWM waveform parameter determination operation in a BUCK mode under the control of an instruction stored in the storage circuit, specifically comprising the following operation steps:

[0047] Using the relation T ON = T con -T d1 -T △ Determine the conduction time width T of the lower bridge arm switch tube Q2 ON Value, use T ON Determine the high level time or duty cycle of the PWM waveform oscillation circuit output waveform PWM3 corresponding to the third output terminal of the single-chip circuit (11); wherein T △It is T con Time correction value; T d1 is the first dead time between the lower bridge arm switch tube Q2 and the upper bridge arm switch tube Q1;

[0048] Use the output voltage value V of the BUCK circuit provided by the measurement circuit (3) out Adjust the duty cycle of waveform PWM1, and use the on-time of the upper bridge arm switch tube Q1 under the duty cycle as the magnetizing current duration T of the energy storage inductor L1. inj .

[0049] Specifically, see Figure 3 As shown, the conduction time width T of the lower bridge arm switch tube Q2 is used. ON The operation of determining the time parameter of the freewheeling tube driving waveform PWML further includes the following operations:

[0050] Use the conduction time width T of the lower bridge arm switch tube Q2 ON The value determines the high level time width or duty cycle of the freewheeling tube drive waveform PWML.

[0051] Specifically, the freewheeling tube is the lower bridge arm switch tube Q2, and the freewheeling tube driving waveform PWML is the driving waveform of the lower bridge arm switch tube Q2.

[0052] Specifically, the PWML waveform and PWMH waveform given in this embodiment are the on-time waveforms of the lower bridge arm switch tube Q2 and the upper bridge arm switch tube Q1 respectively. The PWML waveform and the PWMH waveform need to be converted by the driving circuit 4 to generate the current and voltage parameters required to drive the lower bridge arm switch tube Q2 and the upper bridge arm switch tube Q1.

[0053] Specifically, T △ The value range is: 1 nanosecond ≤ T △ ≤2000 nanoseconds.

[0054] Furthermore, T △ The value of is calculated based on the freewheeling current duration T under different loads and ambient temperatures. con The statistical distribution of the error between the actual value of the freewheeling current duration of the energy storage inductor is used to determine the value of T con Time correction T △ To ensure that T ON +T d1 = T con -T △ The value of is less than the actual value of the freewheeling current duration of the energy storage inductor; or

[0055] To T con Time correction T △ The freewheeling current duration Tcon The value is between 1% and 20% of the calculated value.

[0056] Specifically, the measuring circuit (3) measures the voltage at the output terminal To of the energy storage coil L1 and the input voltage of the BUCK circuit, see Figure 4 As shown, the measurement circuit (3) measures the voltage at the output terminal To of the energy storage coil L1 as the output terminal voltage V of the energy storage inductor out , the input voltage of the BUCK circuit is measured and the result is used as the input voltage of the energy storage inductor V in ; Measurement circuit (3) Measure the voltage V at the input terminal of the energy storage inductor at the drain of the upper arm switch tube Q1 of the BUCK circuit in The measurement result includes the on-state voltage of the upper bridge arm switch tube Q1.

[0057] The utility model provides a PWM waveform generating circuit for DC-DC conversion, which is characterized by:

[0058] The single-chip computer circuit (11) comprises a freewheeling time determination circuit, which comprises a digital operation circuit and a memory, and the digital operation circuit performs the following operations under the control of an operation instruction from the memory:

[0059] Using the geometric relationship (V in -V out ) / V out =T con / T inj Solve for the follow-up time T con The value of in -V out ) is the voltage across the energy storage inductor L1 in the magnetizing state, V out It is the voltage across the energy storage inductor L1 in the freewheeling state and the output voltage of the BUCK circuit. con is the freewheeling time, T inj is the magnetization time.

[0060] The utility model provides a PWM waveform generating circuit for DC-DC conversion, which is characterized by:

[0061] The AND operation circuit (12) comprises a digital integrated circuit for performing an AND operation.

[0062] Specifically, the digital integrated circuit that performs the "AND" operation includes any one of an "AND" operation circuit and a "NAND" operation circuit.

[0063] The utility model provides a PWM waveform generating circuit for DC-DC conversion, which is characterized by:

[0064] The AND operation circuit (12) comprises a diode D3, a diode D5, and a resistor R1, wherein the cathode of the diode D3 is electrically connected to the third output terminal of the single-chip circuit (11), the cathode of the diode D5 is electrically connected to the second output terminal of the single-chip circuit (11), the anodes of the diode D3 and the diode D5, which are electrically connected to each other, are electrically connected to one end of the resistor R1, and the other end of the resistor R1 is electrically connected to a power supply Vcc.

[0065] Specifically, see Figure 2 As shown, the AND operation circuit (12) comprises a diode D3, a diode D5 and a resistor R1, wherein the cathode of the diode D3 is electrically connected to the third output terminal of the single-chip circuit (11), the cathode of the diode D5 is electrically connected to the second output terminal of the single-chip circuit (11), the anodes of the diode D3 and the diode D5, which are electrically connected to each other, are electrically connected to one end of the resistor R1 and the PWML input terminal of the switch tube drive circuit (2), and the other end of the resistor R1 is electrically connected to the power supply Vcc.

[0066] The PWM waveform generating circuit (1) provided by the utility model can be used to control the upper and lower bridge arm switch tubes of the synchronous BUCK circuit, see Figure 4 As shown, the input end Ti of the inductor L1 is electrically connected to the source of the upper arm switch tube Q1 and the drain of the lower arm switch tube Q2, the output end To of the inductor L1 is electrically connected to the positive electrode of the output capacitor C1 and one end of the current measuring resistor Ri, the other end of the current measuring resistor Ri is electrically connected to the positive output terminal T1 of the BUCK circuit, the negative output terminal T2 of the BUCK circuit is electrically connected to the negative electrode of the output capacitor C1 and the power ground line GND of the BUCK circuit, a bypass diode D1 is connected in parallel between the source and the drain of the upper arm switch tube Q1, a bypass diode D2 is connected in parallel between the source and the drain of the lower arm switch tube Q2, and the input power supply of the BUCK circuit is the battery assembly B2; F2 is a power fuse, and C2 is a power filter capacitor.

[0067] Figure 4 In the embodiment, the measuring circuit (3) measures the voltage at the output terminal To of the energy storage coil L1 and the input voltage of the battery assembly B2 to the BUCK circuit; the measuring circuit (3) measures the voltage at the output terminal To of the energy storage coil L1 as the output terminal voltage V of the energy storage inductor. out , the input voltage of the battery component B2 to the BUCK circuit is measured as the input voltage of the energy storage inductor V in ; Figure 4 In the measurement circuit (3), the voltage V at the input terminal of the energy storage inductor is measured at the drain of the upper arm switch tube Q1 of the BUCK circuit. in The measurement result includes the on-state voltage of the upper bridge arm switch tube Q1.

[0068] The freewheeling time determination circuit included in the single-chip microcomputer circuit (11) obtains the voltage V at the output terminal of the energy storage inductor from the measurement circuit (3). out And the voltage V at the input of the energy storage inductor in The measured value is obtained from the PWM waveform parameter determination circuit included in the single-chip circuit (11) to obtain the conduction time value of the upper bridge arm switch tube Q1, and the conduction time is used as the duration T of the magnetizing current of the energy storage inductor. inj , use V in 、V out , T inj And the relationship (V in -V out ) / V out = T con / T inj , solve for the follow-up time T con , and the freewheeling time T con The value is sent to the PWM waveform parameter determination circuit included in the single chip microcomputer circuit (11).

[0069] The PWM waveform parameter determination circuit included in the single-chip microcomputer circuit (11) sends the duration T of the inductor magnetizing current to the freewheeling time determination circuit included in the single-chip microcomputer circuit (11). inj The value of the freewheeling time T is received from the freewheeling time determination circuit con The value of the freewheeling time T con The value of determines the time parameter of the freewheeling tube Q2 driving waveform PWML. The PWM waveform generating circuit (1) uses the PWM waveform parameter determining circuit to inj The PWMH waveform is determined by the value of T con The PWML waveform determined by the value of is sent to the switch tube drive circuit (2).

[0070] The switch tube driving circuit (2) converts the PWMH sent by the PWM waveform generating circuit (1) into a signal form HO required for driving the upper bridge arm switch tube Q1, and converts the PWML sent by the PWM waveform generating circuit (1) into a signal form LO required for driving the lower bridge arm switch tube Q2.

[0071] The PWM waveform generating circuit (1) provided by the utility model can be used to control the upper and lower bridge arm switch tubes of the synchronous BOOST circuit, see Figure 5As shown in the figure, the output end To of the inductor L1 is electrically connected to the source of the upper bridge arm switch tube Q1 and the drain of the lower bridge arm switch tube Q2, the input end Ti of the inductor L1 is electrically connected to the positive electrode of the power supply filter capacitor C1 and the positive electrode of the battery assembly B2, the drain of the upper bridge arm switch tube Q1 is electrically connected to the positive electrode of the output capacitor C2 and one end of the current measuring resistor Ri, the other end of the current measuring resistor Ri is electrically connected to the positive output terminal T1 of the BOOST circuit, the negative output terminal T2 of the BOOST circuit is electrically connected to the negative electrode of the output capacitor C2 and the power ground line GND of the BOOST circuit, a bypass diode D1 is connected in parallel between the source and the drain of the upper bridge arm switch tube Q1, a bypass diode D2 is connected in parallel between the source and the drain of the lower bridge arm switch tube Q2, and the input power supply of the BOOST circuit is the battery assembly B1; F1 is a power fuse.

[0072] When the PWM waveform generating circuit (1) provided by the utility model is used for BOOST circuit driving, refer to Figure 5 As shown, the PWML output terminal of the PWM waveform generating circuit (1) is electrically connected to the PWML input terminal of the switch tube driving circuit (2), and the LO output terminal of the switch tube driving circuit (2) corresponding to the PWML input terminal is electrically connected to the gate of the upper bridge arm switch tube Q1 of the BOOST circuit; the PWMH output terminal of the PWM waveform generating circuit (1) is electrically connected to the PWMH input terminal of the switch tube driving circuit (2), and the HO output terminal of the switch tube driving circuit (2) corresponding to the PWMH input terminal is electrically connected to the gate of the lower bridge arm switch tube Q2 of the BOOST circuit.

[0073] In BOOST mode, the PWM waveform generation circuit (1) uses the geometric relationship V in2 / (V out2 -V in2 ) = T con / T inj Solve for the follow-up time T con The value of V in2 is the voltage across the energy storage inductor L1 in the magnetized state in BOOST mode, and is also the input voltage of the battery pack B1 to the BOOST circuit, (V out2 -V in2 ) is the voltage across the energy storage inductor L1 in the freewheeling state, V out2 is the output voltage of the BOOST circuit, T con is the freewheeling time of the energy storage inductor L1, T inj It is the magnetization time of the energy storage inductor L1.

[0074] See also Figure 5As shown, the measuring circuit (3) measures the drain voltage of the upper bridge arm switch tube Q1, and the measured data is used as the measured voltage of the output terminal To of the energy storage coil L1; the measuring circuit (3) measures the input voltage of the battery assembly B1 to the BOOST circuit; the measuring circuit (3) measures the voltage measurement result of the output terminal To of the energy storage coil L1 as the output terminal voltage V out2 , the input voltage of the battery component B2 to the BOOST circuit is measured as the input voltage of the energy storage inductor V in2 ; Figure 5 In the measurement circuit (3), the voltage V at the output terminal of the energy storage inductor is measured at the drain of the upper bridge arm switch tube Q1 of the BOOST circuit. out2 The measurement result includes the on-state voltage of the upper bridge arm switch tube Q1.

[0075] In the BOOST mode, the PWM waveform generation circuit (1) adjusts the magnetizing time of the energy storage inductor L1 according to the drain voltage measurement result of the upper bridge arm switch tube Q1 and the target value of the BOOST circuit output voltage measured by the measurement circuit (3), that is, the magnetizing current duration T of the energy storage inductor L1 is adjusted. inj Adjustment is performed, that is, the duty cycle of the magnetization time of the energy storage inductor L1 is adjusted; the specific adjustment steps include: adjusting the conduction time of the lower bridge arm switch tube Q1 by adjusting the duty cycle of the waveform PWM1.

[0076] When the PWM waveform generating circuit (1) is used to drive the switch tube of the BOOST circuit, the PWMH waveform output by the PWM waveform generating circuit (1) is used to drive the lower bridge arm switch tube Q2, and the PWML waveform output by the PWM waveform generating circuit (1) is used to drive the upper bridge arm switch tube Q1.

[0077] The technical principle of the present invention is described above in combination with specific embodiments. These descriptions are only for explaining the principle of the present invention and cannot be interpreted as limiting the protection scope of the present invention in any way. Based on the explanations here, technicians in this field can think of other specific implementation methods of the present invention without creative work, and these methods will fall within the protection scope of the present invention.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any technician in the field of the present invention can make any modifications and changes in the form and details of implementation without departing from the spirit and scope disclosed by the present invention, but the scope of protection of the present invention shall be based on the definition of the attached claims.

[0079] The PWM waveform generating circuit for DC-DC conversion provided by the utility model uses a single-chip microcomputer chip with simplified functions and low price to construct the PWM waveform generating circuit for DC-DC conversion, thereby further reducing the manufacturing cost of the DC-DC converter.

Claims

1. A PWM waveform generating circuit for DC-DC conversion, comprising a single chip computer circuit (11) and an AND operation circuit (12); characterized in that: The first output end of the single-chip circuit (11) is configured to output waveform PWM1, the second output end is configured to output waveform PWM2, and the third output end is configured to output waveform PWM3, wherein waveform PWM1 and waveform PWM2 are a pair of pulse waveforms with the same frequency and opposite phases and adjustable duty cycle, waveform PWM3 and waveform PWM2 have the same frequency and different phase conversion time, and the duty cycle of waveform PWM3 is adjustable; The first output terminal of the single-chip circuit (11) is electrically connected to the PWMH input terminal of the switch tube drive circuit (2), and the waveform PWM1 is converted into the switch tube drive waveform HO after being converted by the switch tube drive circuit (2); The second and third output ends of the single-chip circuit (11) are electrically connected to the two input ends of the AND operation circuit (12), respectively; the output end of the AND operation circuit (12) is electrically connected to the PWML input end of the switch tube drive circuit (2); the AND operation circuit (12) performs an AND operation on the waveform PWM2 and the waveform PWM3 to generate a waveform PWML, and the waveform PWML is converted into a switch tube drive waveform LO after being converted by the switch tube drive circuit (2).

2. The PWM waveform generating circuit for DC-DC conversion according to claim 1, characterized in that: The single-chip computer circuit (11) comprises a PWM waveform parameter determination circuit, the PWM waveform parameter determination circuit comprises a digital operation circuit, a storage circuit and a PWM waveform oscillation circuit, the operation circuit performs a PWM waveform parameter determination operation in a BUCK mode under the control of an instruction stored in the storage circuit, specifically comprising the following operation steps: Using the relation T ON = T con -T d1 -T △ Determine the conduction time width T of the lower bridge arm switch tube Q2 ON Value, use T ON Determine the high level time or duty cycle of the PWM waveform oscillation circuit output waveform PWM3 corresponding to the third output terminal of the single-chip circuit (11); wherein T △ It is T con Time correction value; T d1 is the first dead time between the lower bridge arm switch tube Q2 and the upper bridge arm switch tube Q1; Use the output voltage value V of the BUCK circuit provided by the measurement circuit (3) out Adjust the duty cycle of waveform PWM1, and use the on-time of the upper bridge arm switch tube Q1 under the duty cycle as the magnetizing current duration T of the energy storage inductor L1. inj .

3. The PWM waveform generating circuit for DC-DC conversion according to claim 1, characterized in that: The single-chip computer circuit (11) comprises a freewheeling time determination circuit, which comprises a digital operation circuit and a memory, and the digital operation circuit performs the following operations under the control of an operation instruction from the memory: Using the geometric relationship (V in -V out ) / V out =T con / T inj Solve for the follow-up time T con The value of (V in -V out ) is the voltage across the energy storage inductor L1 in the magnetized state, V out It is the voltage across the energy storage inductor L1 in the freewheeling state and the output voltage of the BUCK circuit. con is the freewheeling time, T inj is the magnetization time.

4. The DC-DC conversion PWM waveform generating circuit according to claim 1, characterized in that: The AND operation circuit (12) comprises a digital integrated circuit for performing an AND operation.

5. The PWM waveform generating circuit for DC-DC conversion according to claim 1, characterized in that: The AND operation circuit (12) comprises a diode D3, a diode D5, and a resistor R1; the cathode of the diode D3 is electrically connected to the third output terminal of the single-chip circuit (11); the cathode of the diode D5 is electrically connected to the second output terminal of the single-chip circuit (11); the anodes of the diode D3 and the diode D5, which are electrically connected to each other, are electrically connected to one end of the resistor R1; and the other end of the resistor R1 is electrically connected to a power source Vcc.

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