Frequency-adjustable H-bridge drive circuit
The H-bridge drive circuit that generates square waves through a timer and its peripheral circuits solves the problems of complex circuit structure and insufficient short-circuit protection in the prior art, achieving the effects of simplifying design, reducing costs and improving control accuracy.
Patent Information
- Application Number
- CN202422054688.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-23
- Publication Date
- 2025-09-30
- Estimated Expiration
- 2034-08-23
AI Technical Summary
When testing motors driven at different frequencies, existing H-bridge circuits require an MCU or other device to generate signals, resulting in a complex and costly circuit structure and a lack of effective short-circuit protection.
A timer and its peripheral circuits are used to generate square waves, simplifying the circuit structure. Short-circuit protection is achieved through a current detection circuit, and frequency regulation is achieved by adjusting peripheral circuit parameters, simplifying the control process.
The circuit design is simplified, the cost is reduced, the control accuracy and circuit safety are improved, and efficient short-circuit protection of the frequency-adjustable H-bridge drive circuit is achieved.
Smart Images
Figure CN223402384U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the field of electronic circuits, and in particular relates to an H-bridge driving circuit with adjustable frequency. Background Art
[0002] The H-bridge circuit is a commonly used motor drive circuit that reverses the voltage or current across its connected load or output terminals. This type of circuit can be used for forward and reverse control and speed control of DC motors, stepper motor control, most DC-AC converters (such as inverters and frequency converters) used in power conversion, some DC-DC converters (push-pull converters), and other power electronic devices. An H-bridge typically consists of four independently controlled switching elements, either IGBTs or MOS transistors. In practical applications, it is often necessary to test the state of the switching devices and the motor when driving the motor at different frequencies, thereby testing the system's performance under varying power conditions. Therefore, a frequency-adjustable drive circuit with short-circuit protection is crucial for both practical applications and testing. Utility Model Content
[0003] The utility model provides an H-bridge driving circuit with adjustable frequency. The circuit does not use an MCU or other devices to generate signals, thereby simplifying the circuit structure.
[0004] The driving circuit includes:
[0005] A frequency adjustment circuit is used to generate a square wave according to a set frequency and duty cycle, including a timer and a peripheral circuit for determining the frequency and duty cycle of the square wave generated by the timer;
[0006] A driver chip is used to generate a square wave with the same frequency as the square wave generated by the timer to drive the lower bridge switch unit;
[0007] The push-pull circuit is used to drive the upper bridge switch unit under the drive of the square wave generated by the timer.
[0008] In some embodiments, the output of the timer is connected in series with a resistor R3 for limiting the current of the timer output.
[0009] In some embodiments, a resistor R6 is connected in series to the output of the driver chip, and the square wave generated by the driver chip is connected to the driven switch unit through the resistor R6.
[0010] In some embodiments, the circuit further includes a capacitor C5 for filtering the output of the driver chip and adjusting the switching time.
[0011] In some embodiments, the circuit further includes a resistor R8 for preventing the first electrode and the second electrode of the driven switch unit from being turned on.
[0012] In some embodiments, the output of the push-pull circuit is connected to the driven switch unit via the resistor R5.
[0013] In some embodiments, the circuit further includes a resistor R7 and a voltage regulator diode ZD1 connected in parallel with the resistor R7 for voltage stabilization; the resistor R7 and the resistor R5 are connected in series to divide the voltage so as to maintain the voltage between the second and first electrodes of the driven switch unit.
[0014] In some embodiments, the circuit further includes a current detection circuit, which generates a first trigger signal to shut down the output of the driver chip when an overcurrent occurs in the H-bridge circuit; and generates a second trigger signal to enable the output of the driver chip when an overcurrent does not occur in the H-bridge circuit.
[0015] In some embodiments, the current detection circuit includes a resistor R9 and a comparator.
[0016] In some embodiments, the circuit further includes a low-pass filter for attenuating oscillation and noise between the third pole and the first pole of the switching unit.
[0017] The beneficial effects of the utility model include:
[0018] 1) This drive circuit uses a timer and its peripheral circuits to generate a square wave according to the set operating frequency and duty cycle. It does not use an MCU or other equipment to generate the signal, which simplifies the circuit structure and design process. In addition, the absence of an MCU simplifies circuit control and reduces the cost of circuit application.
[0019] 2) This drive circuit achieves frequency regulation by adjusting peripheral circuit parameters, thereby improving control accuracy.
[0020] 3) The short-circuit protection feedback signal of this drive circuit is not processed by the MCU, but is directly fed back to the drive chip to control the operation of the drive chip, thereby improving the safety and stability of the circuit. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] In order to more clearly illustrate the embodiments of the present application, the following briefly introduces the drawings required for or involved in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. Without inventive work, other drawings can be obtained based on these drawings:
[0022] Figure 1 This is a schematic diagram of the circuit structure of the driving circuit provided by the utility model. DETAILED DESCRIPTION
[0023] This section describes the present invention more fully with reference to the accompanying drawings, which show illustrative embodiments of the present invention. However, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art.
[0024] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and will not be interpreted according to an idealized or very formal meaning unless specifically defined herein.
[0025] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be more thorough and complete and will fully convey the concepts of the example embodiments to those skilled in the art.
[0026] The H-bridge circuit includes four independently controlled switching units, which are IGBTs or MOSs. Figure 1 The utility model provides an H-bridge driving circuit for driving an H-bridge circuit, the circuit comprising:
[0027] A frequency adjustment circuit is used to generate a square wave according to a set frequency and duty cycle, including a timer U1 and a peripheral circuit for determining the frequency and duty cycle of the square wave generated by the timer;
[0028] The driver chip U2 is used to generate a square wave with the same frequency as the square wave generated by the timer to drive the lower bridge switch unit;
[0029] The push-pull circuit is used to drive the upper bridge switch unit under the drive of the square wave generated by the timer.
[0030] This driver circuit drives the frequency-regulating circuit for switching units Q1 and Q3, and the frequency-regulating circuit for driving Q2 and Q4, to generate square waves with the same frequency and opposite phases, ensuring that Q1, Q2 / Q3, and Q4 are not simultaneously conductive. These square waves with the same frequency and opposite phases are generated by two frequency-regulating circuits, but one circuit generates a square wave with an initial positive half-cycle and a positive-negative-positive-negative waveform. The other circuit generates a square wave with an initial negative half-cycle and a negative-positive-negative-positive waveform.
[0031] Please refer to Figure 1In this embodiment, the timer U1 is configured as a NE555 timer, and the peripheral circuit includes an adjustable resistor R1, an adjustable resistor R2, a capacitor C1, and a capacitor C2. NE555 is a bipolar integrated circuit that can generate high-precision timing pulses. It consists of four circuits: a threshold comparator, a trigger comparator, an RS trigger, and an output circuit. The amplitude of its pulse is determined by the 8-pin VCC, such as 5V; the capacitor C2 is usually 0.01uF, and the control voltage pin is grounded after passing through the capacitor C2. The working mode is set to the non-stable mode, and the circuit is automatically triggered. Its frequency and duty cycle are determined by R1, R2, and C1. The high-level pulse width: th = 0.693 × (R1 + R2) × C1 (1); the low-level pulse width: tl = 0.693 × R2 × C1 (2); the frequency: (3) Therefore, by configuring R1, R2, and C1 with different parameters, the timer U1 can generate a square wave with a specified frequency and duty cycle to meet the system requirements.
[0032] The system referred to in this article refers to an H-bridge circuit, and resistor R1, resistor R2, and capacitor C1 are configured according to the operating frequency conditions required by the H-bridge circuit.
[0033] The square wave generated by the timer U1 is connected to the driver chip U2 and the push-pull circuit directly or through the resistor R3 (which limits the current of the output signal of the timer U1OUT pin 3 to achieve circuit protection).
[0034] In this embodiment, the push-pull circuit includes an NPN transistor Q5 and a PNP transistor Q6 to amplify the driving capability.
[0035] This driver circuit's operation is described using P-type switching elements Q1 and Q2 and N-type switching elements Q3 and Q4 as examples: The system's operating frequency and duty cycle are determined, C1 is set to a constant value, and the frequency and duty cycle are adjusted by adjusting the resistances of R1 and R2 to cause U1 to generate a square wave with the specified frequency and duty cycle. Q1 and Q3 are driven as follows: U1's OUT pin 3 outputs a "1," U2 outputs a high level, the voltage on the first terminal of switching element Q3 is high, and switching element Q3 is turned on; NPN transistor Q5 is turned on, and PNP transistor Q6 is turned off. At this point, the voltage on the first terminal of switching element Q1 is high, and Q1 is turned off. When the 3-pin output OUT of U1 in the frequency adjustment circuit of Q1 and Q3 is "1", the 3-pin output OUT of U1 in the frequency adjustment circuit of Q2 and Q4 is "0", U2 outputs a low level, the first pole voltage of the switch unit Q4 is a low level, and the switch unit Q4 is turned off; the NPN transistor Q5 is turned off, and the PNP transistor Q6 is turned on. At this time, the voltage between the first pole and the second pole of the switch unit Q2 is greater than the turn-on voltage, Q2 is turned on, and the current flowing through the load R12 is from right to left.
[0036] When the output OUT of pin 3 of U1 in the frequency adjustment circuit is "0", U2 outputs a low level, the voltage of the first pole of Q3 is 0V, and Q3 is turned off; Q5 is turned off, and Q6 is turned on. At this time, the voltage of the first pole of Q1 is low, and Q1 is turned on. When the output OUT of pin 3 of U1 in the frequency adjustment circuit of Q1 and Q3 is "0", the output OUT of pin 3 of U1 in the frequency adjustment circuit of Q2 and Q4 is "1", U2 outputs a high level, the voltage of the first pole of switch unit Q4 is high, and switch unit Q4 is turned on; NPN transistor Q5 is turned on, and PNP transistor Q6 is turned off. At this time, the potential of the first pole of switch unit Q2 is high, Q2 is turned off, and the current flowing through load R12 is from left to right.
[0037] The drive circuit also includes a current detection circuit, which generates a first trigger signal to turn off the output of the drive chip U2 when there is an overcurrent in the H-bridge circuit; and generates a second trigger signal to turn on the output of the drive chip U2 when there is no overcurrent in the H-bridge circuit.
[0038] Please refer to Figure 1 The current sensing circuit includes comparator U3, resistor R9, capacitor C6, and resistor R4. R9 is the current sensing resistor, typically in the milliohm range. Capacitor C6 maintains the sampling voltage. Comparator U3 receives a reference voltage as its positive input and a voltage across the current sensing resistor as its negative input. When the H-bridge circuit operates normally, when current flows through the low-side switch, a voltage drop occurs across the current sensing resistor that is less than the reference voltage, resulting in a comparator output of 0. When this voltage drop exceeds the threshold voltage, it indicates that the current flowing through the switch exceeds the preset threshold, potentially posing a short circuit risk. In this case, the comparator output is high and fed back to pin 3, SD, of the driver chip U2, shutting down the output. When the SD pin is low, the OUT output is in phase with the input signal, IN. When the SD pin is high, the OUT output is low, shutting down the MOSFET. After shutdown, the SD shutdown control logic will resume only when the SD input signal returns from low to high.
[0039] The current detection circuit operates as follows: When the H-bridge circuit is operating normally, the current flowing through resistor R9 is low, U3's positive input is lower than its negative input, U3 outputs a "0" and this is fed back to U2's SD, allowing U2 to operate normally. In the event of a system short circuit, the current flowing through R9 increases, and U3's positive input voltage increases. When this voltage exceeds the set threshold of 0.5V, U3 outputs a "1" and feeds back a signal to U2's SD. U2 shuts down its driver output until the current decreases and normal operation resumes, then turns it back on, thus providing short-circuit protection for the system.
[0040] The reference voltage connected to the inverting input of comparator U3 is determined by the current flowing through the switch unit and the resistance of the current sense resistor. Within the normal operating range, the current flowing through R9 multiplied by the resistance of R9 is the non-inverting input of comparator U3. When the current flowing through R9 exceeds a certain value, the system is short-circuited. The current value at this point multiplied by the resistance of R9 is the inverting input value, which is also the reference voltage. Under normal operating conditions, the non-inverting input will not exceed the reference voltage, but when a short circuit occurs, the non-inverting input will go high.
[0041] Please refer to Figure 1 The driving circuit further includes a capacitor C3, a capacitor C4, a resistor R6, a capacitor C5, and a resistor R8.
[0042] C3 and C4 are located between the power supply and the ground to perform voltage stabilization and filtering, thereby stabilizing the power supply connected to the driver chip U2.
[0043] The resistor R6 is a driving resistor. The driving chip U2 outputs a square wave with the same frequency as the timer U1. Under the action of the driving resistor R6, a voltage difference is generated and provided to the switch unit Q3.
[0044] Capacitor C5 filters the driving waveform. The capacitor has energy storage performance, which is used to adjust the switching time of the switching unit. Capacitors with different capacitance values have different energy storage and therefore different switching times.
[0045] The resistor R8 is used to prevent conduction between the first electrode and the second electrode of the switch unit. The resistance value of the resistor R8 is selected to be relatively large, so that the current flowing through the resistor R8 is very small.
[0046] Please refer to Figure 1 The driving circuit also includes resistors R5, R7, and a voltage regulator ZD1. R5 is a driving resistor that adjusts the driving speed. Resistor R5 adjusts the switching speed of the switching unit by controlling the flow rate of the charge on the first electrode of the switching unit, as follows:
[0047] 1. Reduce the switching speed (increase the resistance value): Increasing the resistance of the driving resistor will slow down the accumulation and dissipation of the first-pole charge, making the speed at which the switching unit enters the saturation state (on) or cut-off state (off) slower.
[0048] 2. Increase switching speed (reduce resistance value): Reducing the resistance of the driving resistor can accelerate the charging and discharging process of the first-stage charge, allowing the switch unit to enter the saturation state (on) or cutoff state (off) more quickly. This can significantly increase switching speed and reduce turn-on and turn-off time.
[0049] R7 is a voltage dividing resistor, which is connected in series with R5 to divide the voltage so that the voltage between the second pole and the first pole of the switch unit is maintained at a set value and stabilized by the voltage regulator ZD1.
[0050] The driving circuit also includes resistors R10, R11, R13, R14, capacitors C7, C8, C9, and C10; R10 is connected in series with C7 to form a low-pass filter, which allows low-frequency signals to pass through and attenuates high-frequency signals, and is used to reduce oscillation and noise between the third and second poles of Q1. Similarly, R13 and C9, R11 and C8, and R14 and C10 are all low-pass filters.
[0051] The "first pole", "second pole" and "third pole" described in this article are G pole, S pole and D pole when the switching unit is MOSFET; when the switching unit is IGBT, the first pole is G pole, E pole and C pole.
[0052] This drive circuit does not use MCU or equipment to generate signals, which simplifies the design process. The frequency and duty cycle are adjusted through the timer, making the system application more convenient. A short-circuit protection circuit is added to the system, and the output of the driver chip is controlled by comparing the voltage value of the current detection resistor with the threshold value, improving the speed of short-circuit protection, and automatically restoring the output when the system is operating normally, enhancing the safety of the system.
[0053] The present disclosure has been described using the aforementioned embodiments. However, the aforementioned embodiments are merely exemplary embodiments of the present disclosure. It should be noted that the disclosed embodiments do not limit the scope of the present disclosure. On the contrary, modifications and alterations made without departing from the spirit and scope of the present disclosure are within the scope of patent protection of the present disclosure.
Claims
1. A frequency-adjustable H-bridge drive circuit, characterized in that: The driving circuit includes: A frequency adjustment circuit is used to generate a square wave according to a set frequency and duty cycle, including a timer and a peripheral circuit for determining the frequency and duty cycle of the square wave generated by the timer; A driver chip is used to generate a square wave with the same frequency as the square wave generated by the timer to drive the lower bridge switch unit; The push-pull circuit is used to drive the upper bridge switch unit under the drive of the square wave generated by the timer.
2. The frequency-adjustable H-bridge driving circuit according to claim 1, characterized in that: The output of the timer is connected in series with a resistor R3 for limiting the current of the timer output.
3. The frequency-adjustable H-bridge driving circuit according to claim 1, characterized in that: The output of the driving chip is connected in series with a resistor R6 , and the square wave generated by the driving chip is connected to the driven switch unit through the resistor R6 .
4. The frequency-adjustable H-bridge driving circuit according to claim 1, characterized in that: It also includes a capacitor C5 for filtering the output of the driver chip and adjusting the switching time.
5. The frequency-adjustable H-bridge driving circuit according to any one of claims 1 to 4, characterized in that: A resistor R8 is further included to prevent the first and second electrodes of the driven switching unit from being turned on.
6. The frequency-adjustable H-bridge driving circuit according to claim 1, characterized in that: The output of the push-pull circuit is connected to the driven switch unit via the resistor R5.
7. The frequency-adjustable H-bridge driving circuit according to claim 6, characterized in that: It also includes a resistor R7 and a voltage regulator ZD1 connected in parallel with the resistor R7 for voltage stabilization; the resistor R7 and the resistor R5 are connected in series to divide the voltage so as to maintain the voltage between the second electrode and the first electrode of the driven switch unit.
8. The frequency-adjustable H-bridge driving circuit according to claim 1, characterized in that: It also includes a current detection circuit, which generates a first trigger signal to turn off the output of the driver chip when there is overcurrent in the H-bridge circuit; and generates a second trigger signal to enable the driver chip to output when there is no overcurrent in the H-bridge circuit.
9. The frequency-adjustable H-bridge driving circuit according to claim 8, characterized in that: The current detection circuit includes a resistor R9 and a comparator.
10. The frequency-adjustable H-bridge driving circuit according to claim 1, characterized in that: A low-pass filter is also included for attenuating oscillation and noise between the third pole and the first pole of the switching unit.