A signal demodulation circuit and isolation drive circuit

Abstract

The present invention relates to a signal demodulation circuit and an isolation drive circuit. The signal demodulation circuit includes a sampling circuit, a comparison output circuit, and a holding circuit connected in sequence. The first input terminal and the second input terminal of the sampling circuit are respectively used to sample the voltage signal of a first pulse signal and the voltage signal of a second pulse signal generated by a PWM signal modulation module. The comparison output circuit is used to generate a PWM signal based on the magnitude of the voltage signal of the first pulse signal and the voltage signal of the second pulse signal. The holding circuit is used to control the comparison output circuit to output the same PWM signal as the previous moment when the voltage signal of the first pulse signal is equal to the voltage signal of the second pulse signal. The signal demodulation circuit of the present invention can quickly identify pulse signals and has high sampling accuracy. It is applicable to a wide range of high-speed signal demodulation fields.

Description

Technical Field

[0001] The present invention relates to the field of circuit technology, and in particular to a signal demodulation circuit and an isolation drive circuit. Background Art

[0002] Power electronics technology is gradually developing towards higher power density. In the field of switching power supplies, the factor that limits the improvement of product power density is often the inability to reduce the size of magnetic components. In order to reduce the size of magnetic components, the industry generally modulates the PWM signal that needs to be transmitted through transformer magnetic isolation into a pulse signal. The transformer only needs to transmit the pulse signal with a small duty cycle and demodulate it into the original PWM signal. This can not only achieve isolated signal transmission, but also reduce the size of magnetic components, ensuring signal transmission while greatly reducing product volume.

[0003] The industry has already researched related technologies. Patent No. CN201310227192.5, "A Pulse Modulation Magnetic Isolation Drive Circuit," proposes a pulse modulation magnetic isolation drive circuit that modulates a PWM signal, magnetically isolates it, and demodulates it before driving the power transistors on and off. However, the demodulation circuit in this patent primarily consists of diodes and transistors. This is limited by the switching speed of the transistors, resulting in a slow demodulation speed. Furthermore, reliable transistor switching is essential to demodulate the signal. Consequently, the voltage recognition accuracy of the input signal is low, making it unsuitable for high-frequency, high-precision applications. Patent No. CN201110248528.7, "A Magnetic Isolation Drive Circuit," proposes a circuit suitable for applications with a wide duty cycle range and complex drive control. This circuit still requires a transformer pulse signal to turn on the MOSFETs in the demodulation circuit to achieve signal isolation and demodulation transmission. While the turn-on speed of MOSFETs is significantly improved compared to transistors, the signal demodulation speed of this circuit is still limited by the MOSFET's turn-on speed, making it unsuitable for high-frequency applications. Summary of the Invention

[0004] In order to solve at least one of the above-mentioned defects in the prior art, the present invention provides a signal demodulation circuit and an isolation drive circuit, which can quickly identify pulse signals and have high sampling accuracy, and can be applied to the field of wide-range high-speed signal demodulation.

[0005] In order to solve the above problems, the technical solutions adopted by the present invention are as follows:

[0006] In a first aspect, a signal demodulation circuit is provided, which is applied to an isolation drive circuit, wherein the isolation drive circuit includes a PWM signal modulation module and an isolation transformer, and the signal demodulation circuit includes a sampling circuit, a comparison output circuit, and a holding circuit;

[0007] The first input end of the sampling circuit is used to be connected to one end of the secondary winding of the isolation transformer, and is used to sample the voltage signal of the first pulse signal generated by the PWM signal modulation module; the second input end of the sampling circuit is used to be connected to one end of the secondary winding of the isolation transformer, and is used to sample the voltage signal of the second pulse signal generated by the PWM signal modulation module; the first output end of the sampling circuit is connected to the first input end of the comparison output circuit and the first output end of the holding circuit, and the second output end of the sampling circuit is connected to the second output end of the comparison output circuit and the second output end of the holding circuit;

[0008] The output end of the comparison output circuit is connected to the input end of the holding circuit and serves as the output end of the signal demodulation circuit, and is used to generate a PWM signal according to the magnitude of the voltage signal of the first pulse signal and the voltage signal of the second pulse signal;

[0009] The power supply end of the holding circuit is used to be connected to a power supply, and is used to control the comparison output circuit to output the same PWM signal as the previous moment when the voltage signal of the first pulse signal is equal to the voltage signal of the second pulse signal.

[0010] Preferably, the comparison output circuit is used to generate a PWM signal according to the magnitude of the voltage signal of the first pulse signal and the voltage signal of the second pulse signal, including:

[0011] When the comparison output circuit determines that the voltage signal of the first pulse signal is greater than the voltage signal of the second pulse signal, a high-level PWM signal is generated;

[0012] When the comparison output circuit determines that the voltage signal of the first pulse signal is lower than the voltage signal of the second pulse signal, a low-level PWM signal is generated.

[0013] Preferably, the comparison output circuit is a comparator U2, the positive input terminal of the comparator U2 serves as the first input terminal of the comparison output circuit, the negative input terminal serves as the second input terminal of the comparison output circuit, and the output terminal serves as the output terminal of the comparison output circuit.

[0014] Preferably, the holding circuit includes a diode D1, a diode D2, a resistor R3, a resistor R4 and a reverse signal processing unit U1; after one end of the resistor R3 is connected to one end of the resistor R4 and the input end of the reverse signal processing unit U1, it is connected to the output end of the comparison output circuit as the input end of the holding circuit; after the other end of the resistor R4 is connected to the anode of the diode D1, it is connected to the first input end of the comparison output circuit as the first output end of the holding circuit; after the output end of the reverse signal processing unit U1 is connected to the anode of the diode D2, it is connected to the second input end of the comparison output circuit as the second output end of the holding circuit; the other end of the resistor R3, the cathode of the diode D1, and the cathode of the diode D2 serve as the power supply end of the holding circuit, which is used to be connected to a power supply.

[0015] Preferably, the sampling circuit includes a resistor R1, a resistor R2, a capacitor C1, and a capacitor C2. After one end of the resistor R1 is connected to one end of the capacitor C1, it serves as the first input end of the sampling circuit; after the other end of the resistor R1 is connected to one end of the capacitor C2, it serves as the first output end of the sampling circuit; after one end of the resistor R2 is connected to the other end of the capacitor C1, it serves as the second input end of the sampling circuit; after the other end of the resistor R2 is connected to the other end of the capacitor C2, it serves as the second output end of the sampling circuit.

[0016] In a second aspect, a signal demodulation circuit is provided, which is applied to an isolation drive circuit, wherein the isolation drive circuit includes a PWM signal modulation module and an isolation transformer, and the signal demodulation circuit includes: a sampling circuit, a comparison output circuit, and a holding circuit;

[0017] The sampling circuit includes a resistor R1, a resistor R2, a capacitor C1 and a capacitor C2;

[0018] The comparison output circuit includes a comparator U2;

[0019] The holding circuit includes a diode D1, a diode D2, a resistor R3, a resistor R4 and a reverse signal processing unit U1;

[0020] After one end of the resistor R1 is connected to one end of the capacitor C1, it serves as the first input end of the signal demodulation circuit and is connected to one end of the secondary winding of the isolation transformer for sampling the first pulse signal generated by the PWM signal modulation module; the other end of the resistor R1 is connected to one end of the capacitor C2, the anode of the diode D1, one end of the resistor R4, and the positive input end of the comparator U2; after one end of the resistor R2 is connected to the other end of the capacitor C1, it serves as the second input end of the signal demodulation circuit and is connected to one end of the secondary winding of the isolation transformer for sampling the second pulse signal generated by the PWM signal modulation module; the other end of the resistor R2 is connected to the other end of the capacitor C2, the anode of the diode D2, the output end of the reverse signal processing unit U1, and the reverse input end of the comparator U2; after the output end of the comparator U2 is connected to the other end of the resistor R4, one end of the resistor R3, and the input end of the reverse signal processing unit U1, it serves as the output end of the signal demodulation unit; the cathode of the diode D1, the cathode of the diode D2, and the other end of the resistor R3 are used to be connected to the power supply.

[0021] In a third aspect, an isolation drive circuit is provided, comprising a PWM signal modulation module, an isolation transformer and the signal demodulation circuit as described above; the input end of the PWM signal modulation module is used to access the PWM signal, and the output end is connected to the primary winding of the isolation transformer; the secondary winding of the isolation transformer is connected to the input end of the signal demodulation circuit.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention can quickly sample the pulse signal of the input interface. Compared with the traditional demodulation circuit, the relevant switch tube (transistor or MOS tube) in the demodulation circuit needs to be turned on to sample the input pulse signal. The present invention only needs a voltage difference between the two interfaces at the input end. The pulse signal can be quickly identified through the sampling resistor and capacitor, achieving the effect of high-speed sampling, and can be applied to higher-frequency signal transmission occasions; at the same time, the circuit only samples the voltage signal, has high sampling accuracy, and the circuit structure is simple, which is conducive to improving the power density of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 1 is a circuit schematic diagram of a signal demodulation circuit of the present invention;

[0025] Figure 2 This is the pulse signal and demodulation signal waveform of the present invention. DETAILED DESCRIPTION

[0026] like Figure 1As shown, in this embodiment, a signal demodulation circuit is provided, which is applied to an isolation drive circuit. The isolation drive circuit includes a PWM signal modulation module and an isolation transformer. The signal demodulation circuit includes a sampling circuit, a comparison output circuit and a holding circuit.

[0027] The first input end of the sampling circuit is used to be connected to one end of the secondary winding of the isolation transformer, and is used to sample the voltage signal of the first pulse signal generated by the PWM signal modulation module; the second input end of the sampling circuit is used to be connected to one end of the secondary winding of the isolation transformer, and is used to sample the voltage signal of the second pulse signal generated by the PWM signal modulation module; the first output end of the sampling circuit is connected to the first input end of the comparison output circuit and the first output end of the holding circuit, and the second output end of the sampling circuit is connected to the second output end of the comparison output circuit and the second output end of the holding circuit;

[0028] The output end of the comparison output circuit is connected to the input end of the holding circuit and serves as the output end of the signal demodulation circuit, and is used to generate a PWM signal according to the magnitude of the voltage signal of the first pulse signal and the voltage signal of the second pulse signal;

[0029] The power supply end of the holding circuit is used to be connected to the power supply VCC, and is used to control the comparison output circuit to output the same PWM signal as the previous moment when the voltage signal of the first pulse signal is equal to the voltage signal of the second pulse signal.

[0030] In this embodiment, the comparison output circuit is used to generate a PWM signal according to the magnitude of the voltage signal of the first pulse signal and the voltage signal of the second pulse signal, including:

[0031] When the comparison output circuit determines that the voltage signal of the first pulse signal is greater than the voltage signal of the second pulse signal, a high-level PWM signal is generated;

[0032] When the comparison output circuit determines that the voltage signal of the first pulse signal is lower than the voltage signal of the second pulse signal, a low-level PWM signal is generated.

[0033] Specifically, after the first input end of the sampling circuit collects the first pulse signal transmitted by the isolation transformer, the first pulse signal is transmitted to the first input end of the comparison output circuit. After the second input end of the sampling circuit collects the second pulse signal transmitted by the isolation transformer, the second pulse signal is transmitted to the second input end of the comparison output circuit. In a specific embodiment, the first pulse signal is a positive pulse signal, and the second pulse signal is a negative pulse signal. The first pulse signal and the second pulse signal are generated by the PWM signal modulation module according to the received PWM signal modulation; the comparison output circuit compares the voltage signal of the first pulse signal and the voltage signal of the second pulse. When it is determined that the voltage signal of the first pulse signal is greater than the voltage signal of the second pulse signal, a high-level PWM signal is output. When it is determined that the voltage signal of the first pulse signal is greater than the voltage signal of the second pulse signal, a high-level PWM signal is output. When the voltage signal of the pulse signal is equal to the voltage signal of the second pulse signal, a low-level PWM signal is output. When it is determined that the voltage signal of the first pulse signal is equal to the voltage signal of the second pulse signal, the holding circuit controls the comparison output circuit to output the same PWM signal as the previous moment, that is, when the previous moment is a high level, the holding circuit controls the comparison output circuit to output a high-level PWM signal, and when the previous moment is a low level, the holding circuit controls the comparison output circuit to output a low-level PWM signal, until the voltage signal sizes of the first pulse signal and the second pulse signal are different. Therefore, the signal demodulation circuit described in this embodiment only needs a voltage difference between the pulse signals collected by the first input terminal and the second input terminal to quickly identify the pulse signal and demodulate the pulse signal into a PWM signal. It has fast speed and high accuracy and can be used in higher frequency signal transmission occasions.

[0034] As a specific implementation of the comparison output circuit, the comparison output circuit is a comparator U2, the positive input terminal of the comparator U2 serves as the first input terminal of the comparison output circuit, the reverse input terminal serves as the second input terminal of the comparison output circuit, and the output terminal serves as the output terminal of the comparison output circuit.

[0035] As a specific embodiment of the holding circuit, the holding circuit includes a diode D1, a diode D2, a resistor R3, a resistor R4 and a reverse signal processing unit U1; one end of the resistor R3 is connected to one end of the resistor R4 and the input end of the reverse signal processing unit U1, and then connected to the output end of the comparison output circuit as the input end of the holding circuit; the other end of the resistor R4 is connected to the anode of the diode D1, and then connected to the first input end of the comparison output circuit as the first output end of the holding circuit; the output end of the reverse signal processing unit U1 is connected to the anode of the diode D2, and then connected to the second input end of the comparison output circuit as the second output end of the holding circuit; the other end of the resistor R3, the cathode of the diode D1, and the cathode of the diode D2 serve as the power supply end of the holding circuit, and are used to be connected to the power supply VCC.

[0036] Specifically, diode D1 is a pull-up diode in the same direction, and diode D2 is a pull-up diode in the opposite direction, which plays the role of clamping voltage; resistor R3 is a pull-up resistor, and resistor R4 is a feedback resistor. When the output end of comparator U2 is at a high level, resistor R3 and resistor R4 pull up the non-inverting input end of comparator U2 to a high level. When the output end of comparator U2 is at a low level, resistor R4 pulls down the non-inverting input end of comparator U2 to a low level. The reverse signal processing unit U1 can be, but is not limited to, a logic processing unit such as an AND gate or an OR gate. When the output end of comparator U2 is at a high level, the reverse signal processing unit U1 pulls down the reverse input end of comparator U2 to a low level. When the output end of comparator U2 is at a low level, the reverse signal processing unit U1 pulls up the reverse input end of comparator U2 to a high level.

[0037] As a specific embodiment of the sampling circuit, the sampling circuit includes a resistor R1, a resistor R2, a capacitor C1 and a capacitor C2. After one end of the resistor R1 is connected to one end of the capacitor C1, it serves as the first input end of the sampling circuit; after the other end of the resistor R1 is connected to one end of the capacitor C2, it serves as the first output end of the sampling circuit; after one end of the resistor R2 is connected to the other end of the capacitor C1, it serves as the second input end of the sampling circuit; after the other end of the resistor R2 is connected to the other end of the capacitor C2, it serves as the second output end of the sampling circuit.

[0038] Specifically, resistor R1 and resistor R2 are both sampling resistors, and capacitor C1 and capacitor C2 are both sampling capacitors. By using resistor R1, resistor R2, capacitor C1 and capacitor C2 as a sampling circuit, as long as there is a voltage difference between the first input terminal and the second input terminal of the sampling circuit, the pulse signal can be quickly identified to achieve the effect of high-speed sampling. In addition, resistor R1, resistor R2, capacitor C1 and capacitor C2 can filter out the interference of high-frequency noise on the signal, thereby improving sampling accuracy and anti-interference performance.

[0039] The specific circuit connection method of this embodiment is:

[0040] One end of resistor R1 is connected to one end of capacitor C1 and serves as the first input terminal of the signal demodulation circuit for connecting to one end of the secondary winding of the isolation transformer to sample the first pulse signal generated by the PWM signal modulation module; the other end of resistor R1 is connected to one end of capacitor C2, the anode of diode D1, one end of resistor R4, and the non-inverting input terminal of comparator U2; one end of resistor R2 is connected to the other end of capacitor C1 and serves as the second input terminal of the signal demodulation circuit for connecting to one end of the secondary winding of the isolation transformer to sample the second pulse signal generated by the PWM signal modulation module; the other end of resistor R2 is connected to the other end of capacitor C2, the anode of diode D2, the output terminal of the reverse signal processing unit U1, and the inverting input terminal of comparator U2. The output terminal of comparator U2 is connected to the other end of resistor R4, one end of resistor R3, and the input terminal of the reverse signal processing unit U1 and serves as the output terminal of the signal demodulation unit; the cathodes of diode D1 and diode D2 and the other end of resistor R3 are used to connect to the power supply VCC.

[0041] The following combines Figure 1 and Figure 2 , and specifically describes the working process of the signal demodulation circuit in this embodiment. Here, Vin+ is the voltage signal waveform of the first pulse signal sampled by the first input terminal of the sampling circuit, Vin- is the voltage signal waveform of the second pulse signal sampled by the second input terminal of the sampling circuit, Vin+- is the waveform of Vin+ with Vin- as the reference, and PWM is the waveform output by comparator U2;

[0042] [t0~t1]: Vin+ > Vin-, the voltage V3 at the non-inverting input terminal of comparator U2 is greater than the voltage V1 at the inverting input terminal, and the output of comparator U2 is high level;

[0043] [t1~t2]: Vin+ = Vin-. Due to the functions of resistor R3 and resistor R4, the voltage V3 at the non-inverting input terminal of comparator U2 is pulled up to high level, and the voltage V1 at the inverting input terminal of comparator U2 is pulled down to low level due to the function of the reverse signal processing unit U1. The voltage V3 at the non-inverting input terminal is greater than the voltage V1 at the inverting input terminal, and the output of comparator U2 is high level;

[0044] [t2~t3]: Vin+ < Vin-, the voltage V3 at the non-inverting input terminal of comparator U2 is less than the voltage V1 at the inverting input terminal, and the output of comparator U2 is low level;

[0045] [t3~t4]: Vin+=Vin-. Due to the action of resistor R4, the voltage V3 of the non-inverting input terminal of the comparator U2 is pulled down to a low level. The voltage V1 of the reverse input terminal of the comparator U2 is pulled up to a high level due to the action of the reverse signal processing unit U1. The voltage V3 of the non-inverting input terminal is less than the voltage V1 of the reverse input terminal, and the output of the comparator U2 is a low level.

[0046] The description of the above embodiments is only used to help understand the inventive concept of this application and is not intended to limit the present invention. For ordinary technicians in this technical field, any modifications, equivalent substitutions, improvements, etc. made without departing from the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A signal demodulation circuit, applied to an isolation drive circuit, wherein the isolation drive circuit comprises a PWM signal modulation module and an isolation transformer, characterized in that: The signal demodulation circuit includes a sampling circuit, a comparison output circuit and a holding circuit; The first input end of the sampling circuit is used to be connected to one end of the secondary winding of the isolation transformer, and is used to sample the voltage signal of the first pulse signal generated by the PWM signal modulation module; the second input end of the sampling circuit is used to be connected to one end of the secondary winding of the isolation transformer, and is used to sample the voltage signal of the second pulse signal generated by the PWM signal modulation module; the first output end of the sampling circuit is connected to the first input end of the comparison output circuit and the first output end of the holding circuit, and the second output end of the sampling circuit is connected to the second output end of the comparison output circuit and the second output end of the holding circuit; The output end of the comparison output circuit is connected to the input end of the holding circuit and serves as the output end of the signal demodulation circuit, and is used to generate a PWM signal according to the magnitude of the voltage signal of the first pulse signal and the voltage signal of the second pulse signal; The power supply end of the holding circuit is used to be connected to a power supply, and is used to control the comparison output circuit to output the same PWM signal as the previous moment when the voltage signal of the first pulse signal is equal to the voltage signal of the second pulse signal; The holding circuit includes a diode D1, a diode D2, a resistor R3, a resistor R4, and a reverse signal processing unit U1; one end of the resistor R3 is connected to one end of the resistor R4 and the input end of the reverse signal processing unit U1, and then serves as the input end of the holding circuit and is connected to the output end of the comparison output circuit; the other end of the resistor R4 is connected to the anode of the diode D1, and then serves as the first output end of the holding circuit and is connected to the first input end of the comparison output circuit; the output end of the reverse signal processing unit U1 is connected to the anode of the diode D2, and then serves as the second output end of the holding circuit and is connected to the second input end of the comparison output circuit; the other end of the resistor R3, the cathode of the diode D1, and the cathode of the diode D2 serve as the power supply end of the holding circuit and are used to be connected to a power supply; The sampling circuit includes a resistor R1, a resistor R2, a capacitor C1, and a capacitor C2. One end of the resistor R1 is connected to one end of the capacitor C1 to serve as a first input end of the sampling circuit; the other end of the resistor R1 is connected to one end of the capacitor C2 to serve as a first output end of the sampling circuit; one end of the resistor R2 is connected to the other end of the capacitor C1 to serve as a second input end of the sampling circuit; and the other end of the resistor R2 is connected to the other end of the capacitor C2 to serve as a second output end of the sampling circuit.

2. The signal demodulation circuit according to claim 1, wherein: The comparison output circuit is used to generate a PWM signal according to the magnitude of the voltage signal of the first pulse signal and the voltage signal of the second pulse signal, and includes: When the comparison output circuit determines that the voltage signal of the first pulse signal is greater than the voltage signal of the second pulse signal, a high-level PWM signal is generated; When the comparison output circuit determines that the voltage signal of the first pulse signal is lower than the voltage signal of the second pulse signal, a low-level PWM signal is generated.

3. The signal demodulation circuit according to claim 1, wherein: The comparison output circuit is a comparator U2, the positive input terminal of the comparator U2 serves as the first input terminal of the comparison output circuit, the negative input terminal serves as the second input terminal of the comparison output circuit, and the output terminal serves as the output terminal of the comparison output circuit.

4. A signal demodulation circuit, applied to an isolation drive circuit, wherein the isolation drive circuit comprises a PWM signal modulation module and an isolation transformer, characterized in that: The signal demodulation circuit includes: a sampling circuit, a comparison output circuit and a holding circuit; The sampling circuit includes a resistor R1, a resistor R2, a capacitor C1 and a capacitor C2; The comparison output circuit includes a comparator U2; The holding circuit includes a diode D1, a diode D2, a resistor R3, a resistor R4 and a reverse signal processing unit U1; After one end of the resistor R1 is connected to one end of the capacitor C1, it serves as the first input end of the signal demodulation circuit and is connected to one end of the secondary winding of the isolation transformer for sampling the first pulse signal generated by the PWM signal modulation module; the other end of the resistor R1 is connected to one end of the capacitor C2, the anode of the diode D1, one end of the resistor R4, and the positive input end of the comparator U2; after one end of the resistor R2 is connected to the other end of the capacitor C1, it serves as the second input end of the signal demodulation circuit and is connected to one end of the secondary winding of the isolation transformer for sampling the second pulse signal generated by the PWM signal modulation module; the other end of the resistor R2 is connected to the other end of the capacitor C2, the anode of the diode D2, the output end of the reverse signal processing unit U1, and the reverse input end of the comparator U2; after the output end of the comparator U2 is connected to the other end of the resistor R4, one end of the resistor R3, and the input end of the reverse signal processing unit U1, it serves as the output end of the signal demodulation circuit; the cathode of the diode D1, the cathode of the diode D2, and the other end of the resistor R3 are used to be connected to the power supply.

5. An isolation drive circuit, characterized in that: It comprises a PWM signal modulation module, an isolation transformer and a signal demodulation circuit according to any one of claims 1 to 4; the input end of the PWM signal modulation module is used to receive the PWM signal, and the output end is connected to the primary winding of the isolation transformer; the secondary winding of the isolation transformer is connected to the input end of the signal demodulation circuit.

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