Control voltage conversion circuit based on isolation transformer and electric appliance applying same

Abstract

The application discloses a control voltage conversion circuit based on an isolation transformer and an electric appliance applying the same. The control voltage conversion circuit based on the isolation transformer comprises an overvoltage protection module for overvoltage protection of an input voltage, a hysteresis comparison output module for providing a forward reference voltage, and a primary feedback module for outputting a feedback voltage according to the forward reference voltage and the input voltage. The control voltage conversion circuit based on the isolation transformer eliminates high-voltage breakdown due to interference, protects a control circuit, establishes a static working point, realizes safe isolation control and electric signal transmission, and achieves the purpose of safe control.

Description

Technical Field

[0001] This invention belongs to the field of voltage conversion technology, specifically relating to a control voltage conversion circuit based on an isolation transformer and electrical equipment using the same. Background Technology

[0002] When sampling and controlling voltage conversion for home appliances such as range hoods and steam ovens, the market often uses long-distance transmission of voltage divider resistors and microcontroller sampling.

[0003] However, this method of controlling voltage conversion has disadvantages such as excessive line loss resistance (if the sensor requires a long line connection), inaccurate signal acquisition, lack of isolation control to ensure safety, and limited application range. In the past, R&D personnel or enterprises have neglected to innovate and improve this part of the application due to sticking to old ways and limitations in technological advancement, which directly led to objective phenomena such as high product repair rate, poor customer experience, and decline in brand quality. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a control voltage conversion circuit based on an isolation transformer, which enables safe isolation control and electrical signal transmission, thereby achieving the purpose of safe control.

[0005] Another object of the present invention is to provide an electrical device.

[0006] The technical solution adopted in this invention is:

[0007] A control voltage conversion circuit based on an isolation transformer includes an overvoltage protection module for overvoltage protection of the input voltage, a hysteresis comparator output module for providing a positive reference voltage, and a primary feedback module for outputting a feedback voltage based on the positive reference voltage and the input voltage. The overvoltage protection module and the hysteresis comparator output module are both electrically connected to the primary feedback module.

[0008] Preferably, the overvoltage protection module includes an overvoltage protection unit, a low-pass filter unit, a bias voltage unit, and a rectifier bridge unit, wherein the overvoltage protection unit is electrically connected to the low-pass filter unit, the bias voltage unit, and the rectifier bridge unit in sequence.

[0009] Preferably, the overvoltage protection unit includes a first Zener diode ZD1, a first resistor R1, a first capacitor C1, a second capacitor C2, and a first transistor Q1. One end of the first Zener diode ZD1, one end of the first capacitor C1, and the collector of the first transistor Q1 are all electrically connected to the positive input voltage VIN+. The other end of the first Zener diode ZD1, the other end of the first capacitor C1, and the base of the first transistor Q1 are all electrically connected to the negative input voltage VIN-, one end of the first resistor R1, and one end of the second capacitor C2. The emitter of the first transistor Q1, the other end of the first resistor R1, and the other end of the second capacitor C2 are connected.

[0010] Preferably, the low-pass filter unit includes a second resistor R2 and a third capacitor C3. One end of the second resistor R2 is electrically connected to the positive terminal VIN+ of the input voltage, and the other end of the second resistor R2 is electrically connected to one end of the third capacitor C3. The other end of the third capacitor C3 is electrically connected to the emitter of the first transistor Q1.

[0011] Preferably, the bias voltage unit includes a first diode D1 and a second diode D2. The negative terminal of the first diode D1 is connected to the common connection terminal of the second resistor R2 and the third capacitor C3, and the positive terminal of the second diode D2 is connected to the common connection terminal of the third capacitor C3, the first transistor Q1, the first resistor R1 and the second capacitor C2.

[0012] Preferably, the rectifier bridge unit includes a third diode D3, a fourth diode D4, a fifth diode D5, and a sixth diode D6. The cathodes of the third diode D3 and the fifth diode D5 are both electrically connected to the anode of the first diode D1. The anode of the third diode D3 is electrically connected to the cathode of the fourth diode D4. The anode of the fifth diode D5 is electrically connected to the cathode of the sixth diode D6. The anodes of the fourth diode D4 and the sixth diode D6 are both electrically connected to the cathode of the second diode D2.

[0013] Preferably, the hysteresis comparator output module includes a hysteresis comparator A1, a third resistor R3, a fourth resistor R4, and a fifth resistor R5. The sixth pin of the hysteresis comparator A1 is connected in series with the third resistor R3 and then connected to a pulse width modulation signal. The fifth pin of the hysteresis comparator A1 is connected in parallel with one end of the fourth resistor R4 and one end of the fifth resistor R5. The other end of the fourth resistor R4 is electrically connected to the frequency conversion voltage VF. The other end of the fifth resistor R5 is electrically connected to the seventh pin of the hysteresis comparator A1 and the primary feedback module.

[0014] Preferably, the primary feedback module includes an isolation transformer T1, a sixth resistor R6, a seventh diode D7, an eighth resistor R8, a second Zener diode ZD2, and a fourth capacitor C4. The first and second pins of the isolation transformer T1 are connected to the overvoltage protection module. The third pin of the isolation transformer T1 is connected to the hysteresis comparator output module and one end of the sixth resistor R6. The other end of the sixth resistor R6 is connected in series with the seventh diode D7 and then in parallel with one end of the second Zener diode ZD2, one end of the seventh resistor R7, and one end of the eighth resistor R8. The other end of the second Zener diode ZD2 is connected to the power supply VCC. The other end of the eighth resistor R8 is connected to the feedback voltage VO and one end of the fourth capacitor C4. The other end of the fourth capacitor C4, the other end of the seventh resistor R7, and the fourth pin of the isolation transformer T1 are all grounded.

[0015] Preferably, the second Zener diode ZD2 is a clamping Zener diode.

[0016] Another technical solution of the present invention is implemented as follows:

[0017] An electrical device comprising the aforementioned control voltage conversion circuit based on an isolation transformer.

[0018] Compared with the prior art, the control voltage conversion circuit based on the isolation transformer of the present invention uses an overvoltage protection module to protect the input voltage from overvoltage, eliminate high voltage breakdown caused by interference, and protect the control circuit. The hysteresis comparison output module provides a positive reference voltage to establish the static operating point. The primary feedback module outputs a feedback voltage based on the positive reference voltage and the input voltage to achieve safe isolation control and electrical signal transmission, thereby achieving the purpose of safe control. Attached Figure Description

[0019] Figure 1 This is a circuit diagram of a control voltage conversion circuit based on an isolation transformer provided in Embodiment 1 of the present invention;

[0020] Figure 2 This is a specific circuit diagram of a control voltage conversion circuit based on an isolation transformer provided in Embodiment 1 of the present invention;

[0021] Figure 3 This is a hysteresis region diagram of the PWM signal of a hysteresis comparator A1 in a control voltage conversion circuit based on an isolation transformer, provided in Embodiment 1 of the present invention.

[0022] Explanation of reference numerals in the attached figures

[0023] 1-Overvoltage protection module, 11-Overvoltage protection unit, 12-Low-pass filter unit, 13-Bias voltage unit, 14-Rectifier bridge unit, 2-Hysteresis comparator output module, 3-Primary feedback module. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0025] Example 1

[0026] This invention provides a control voltage conversion circuit based on an isolation transformer, such as... Figure 1-3As shown, it includes an overvoltage protection module 1 for overvoltage protection of the input voltage, a hysteresis comparison output module 2 for providing a positive reference voltage, and a primary feedback module 3 for outputting a feedback voltage based on the positive reference voltage and the input voltage. The overvoltage protection module 1 and the hysteresis comparison output module 2 are both electrically connected to the primary feedback module 3.

[0027] In this way, the overvoltage protection module 1 is used to protect the input voltage from overvoltage, eliminate high voltage breakdown caused by interference, and protect the control circuit. The hysteresis comparison output module 2 provides a positive reference voltage to establish the static operating point. The primary feedback module 3 outputs a feedback voltage based on the positive reference voltage and the input voltage to achieve safe isolation control and electrical signal transmission, thus achieving the purpose of safe control.

[0028] The overvoltage protection module 1 includes an overvoltage protection unit 11, a low-pass filter unit 12, a bias voltage unit 13, and a rectifier bridge unit 14. The overvoltage protection unit 11 is electrically connected to the low-pass filter unit 12, the bias voltage unit 13, and the rectifier bridge unit 14 in sequence.

[0029] In this way, the overvoltage protection unit 11 provides overvoltage protection for the sensor input voltage, the low-pass filter unit 12 reduces input voltage jitter, the bias voltage unit 13 increases the bias voltage when the sensor input voltage is zero, and the rectifier bridge unit 14 performs rectification.

[0030] The overvoltage protection unit 11 includes a first Zener diode ZD1, a first resistor R1, a first capacitor C1, a second capacitor C2, and a first transistor Q1. One end of the first Zener diode ZD1, one end of the first capacitor C1, and the collector of the first transistor Q1 are all electrically connected to the positive input voltage VIN+. The other end of the first Zener diode ZD1, the other end of the first capacitor C1, and the base of the first transistor Q1 are all electrically connected to the negative input voltage VIN-, one end of the first resistor R1, and one end of the second capacitor C2. The emitter of the first transistor Q1, the other end of the first resistor R1, and the other end of the second capacitor C2 are connected.

[0031] Thus, the circuit is connected through the sensor input voltages VIN+ and VIN-, with a voltage range of 0 to 5V. The circuit consists of the first Zener diode ZD1, the first transistor Q1, and the first resistor R1, forming an overvoltage protection and dummy load circuit.

[0032] When the input voltage is below 6V, the first Zener diode ZD1 is cut off, and the voltage across it is Δ(VIN+~VIN-). Then, the transistor Vce_Q1=Δ(VIN+~VIN-)+Vbe_Q1;

[0033] When the input voltage is higher than 6V, the first Zener diode ZD1 is turned on, and the voltage across it is VZD1. Then, the transistor Vce_Q1 = VZD1 + Vbe_Q1.

[0034] From the above two steps, we know that transistor VCE_Q1 is a dummy load used to dissipate the energy transmitted from the secondary side of isolation transformer T1 and the sensor input voltage. The first capacitor C1 and the second capacitor C2 are filter capacitors between the CBE terminals of the transistor, enhancing the filtering of input interference voltage.

[0035] The low-pass filter unit 12 includes a second resistor R2 and a third capacitor C3. One end of the second resistor R2 is electrically connected to the positive terminal of the input voltage VIN+, and the other end of the second resistor R2 is electrically connected to one end of the third capacitor C3. The other end of the third capacitor C3 is electrically connected to the emitter of the first transistor Q1.

[0036] In this way, the second resistor R2 and the third capacitor C3 form an RC low-pass filter to reduce input voltage jitter.

[0037] The bias voltage unit 13 includes a first diode D1 and a second diode D2. The negative terminal of the first diode D1 is connected to the common connection terminal of the second resistor R2 and the third capacitor C3. The positive terminal of the second diode D2 is connected to the common connection terminal of the third capacitor C3, the first transistor Q1, the first resistor R1 and the second capacitor C2.

[0038] In this way, the bias voltage is increased by the first diode D1 and the second diode D2 when the sensor input voltage Δ(VIN+~VIN-) is 0, ensuring that the bias voltage Vce_Q1 of the secondary side of the isolation transformer T1 (which can also be equivalent to Vce_Q1) is 2*VD1.

[0039] The rectifier bridge unit 14 includes a third diode D3, a fourth diode D4, a fifth diode D5, and a sixth diode D6. The cathodes of the third diode D3 and the fifth diode D5 are both electrically connected to the anode of the first diode D1. The anode of the third diode D3 is electrically connected to the cathode of the fourth diode D4. The anode of the fifth diode D5 is electrically connected to the cathode of the sixth diode D6. The anodes of the fourth diode D4 and the sixth diode D6 are both electrically connected to the cathode of the second diode D2.

[0040] In this way, the input voltage is rectified by forming a rectifier bridge using the third diode D3, the fourth diode D4, the fifth diode D5, and the sixth diode D6.

[0041] From the above steps, we can determine the secondary voltage of isolation transformer T1:

[0042] Vs_T1 = Vce_Q1 + 2*VD1 + 2*VD5 (forward voltage drop of diodes in the rectifier bridge). At this point, the normal operation of the input transmission and overvoltage protection circuit of a sensor is completed.

[0043] The hysteresis comparator output module 2 includes a hysteresis comparator A1, a third resistor R3, a fourth resistor R4, and a fifth resistor R5. The sixth pin of the hysteresis comparator A1 is connected in series with the third resistor R3 and then connected to a pulse width modulation signal (i.e., a PWM signal). The fifth pin of the hysteresis comparator A1 is connected in parallel with one end of the fourth resistor R4 and one end of the fifth resistor R5. The other end of the fourth resistor R4 is electrically connected to the frequency conversion voltage VF. The other end of the fifth resistor R5 is electrically connected to the seventh pin of the hysteresis comparator A1 and the primary feedback module 3.

[0044] Thus, by increasing the positive PWM reference voltage output to the isolation transformer T1 through the hysteresis comparator A1, and configuring the fourth resistor R4 and the fifth resistor R5 according to the virtual short and virtual open circuit conditions, the PWM signal hysteresis region of the hysteresis comparator A1 is achieved as shown in the attached figure. Figure 3 As shown, when the PWM varies between 0 and 5V, the output VO_PWM voltage is 0 / VO_PWM (PWM waveform). After the above steps, the positive PWM output of the primary reference voltage of the isolation transformer T1 is realized.

[0045] The basic principle of pulse width modulation (PWM) is to control the on / off state of the switching devices in the inverter circuit, resulting in a series of pulses of equal amplitude at the output. These pulses replace the sine wave or the desired waveform. In other words, multiple pulses are generated within half a cycle of the output waveform, ensuring that the equivalent voltage of each pulse is a sine wave, resulting in a smooth output with fewer low-order harmonics. By modulating the width of each pulse according to certain rules, both the magnitude of the inverter circuit's output voltage and the output frequency can be changed.

[0046] The primary feedback module 3 includes an isolation transformer T1, a sixth resistor R6, a seventh diode D7, an eighth resistor R8, a second Zener diode ZD2, and a fourth capacitor C4. The first and second pins of the isolation transformer T1 are connected to the overvoltage protection module 1. The third pin of the isolation transformer T1 is connected to the hysteresis comparator output module 2 and one end of the sixth resistor R6. The other end of the sixth resistor R6 is connected in series with the seventh diode D7 and then in parallel with one end of the second Zener diode ZD2, one end of the seventh resistor R7, and one end of the eighth resistor R8. The other end of the second Zener diode ZD2 is connected to the power supply VCC. The other end of the eighth resistor R8 is connected to the feedback voltage VO and one end of the fourth capacitor C4. The other end of the fourth capacitor C4, the other end of the seventh resistor R7, and the fourth pin of the isolation transformer T1 are all grounded.

[0047] Thus, the secondary voltage Vs_T1 of the isolation transformer is obtained through the overvoltage protection module 1. According to the turns ratio of the isolation transformer (the turns ratio is n = 1:1), the primary voltage Vp_T1 of the isolation transformer is n * Vs_T1 = Vs_T1. After rectification by the sixth resistor R6 and the seventh diode D7, a half-wave forward voltage is obtained. The fourth capacitor C4 and the eighth resistor R8 form a low-pass filter. The seventh resistor R7 is a dummy load used to consume the energy of the half-wave forward conduction of the isolation transformer T1. After passing through the low-pass filter, the rectified average feedback voltage VO is obtained and transmitted to the controller for subsequent processing.

[0048] The second Zener diode, ZD2, is a clamping Zener diode.

[0049] Thus, the second Zener diode ZD2 is a clamping Zener diode used for clamping protection when the voltage VO is overvoltage. When VO>VCC, the second Zener diode ZD2 conducts in the forward direction, and VO=VCC+0.7V; when VO<0V, the Zener diode conducts in the reverse direction, and VO is clamped to 0V.

[0050] The control voltage conversion circuit based on the isolation transformer of the present invention uses an overvoltage protection module to protect the input voltage from overvoltage, eliminate high voltage breakdown caused by interference, and protect the control circuit. A hysteresis comparison output module provides a positive reference voltage to establish the static operating point. A primary feedback module outputs a feedback voltage based on the positive reference voltage and the input voltage to achieve safe isolation control and electrical signal transmission, thereby achieving the purpose of safe control.

[0051] Example 2

[0052] Embodiment 2 of the present invention provides an electrical device, which includes the control voltage conversion circuit based on the isolation transformer.

[0053] Among them, electrical equipment includes high-power electrical appliances such as range hoods and steam ovens.

[0054] The electrical equipment of the present invention uses an overvoltage protection module to protect the input voltage from overvoltage, eliminate high-voltage breakdown caused by interference, and protect the control circuit. It provides a positive reference voltage through a hysteresis comparison output module to establish the static operating point. It outputs a feedback voltage through a primary feedback module based on the positive reference voltage and the input voltage to achieve safe isolation control and electrical signal transmission, thereby achieving the purpose of safe control.

[0055] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A control voltage conversion circuit based on an isolation transformer, characterized in that, It includes an overvoltage protection module (1) for overvoltage protection of the input voltage and forming a dummy load circuit, and a hysteresis comparison output module (2) for providing a positive reference voltage to establish the static operating point; And a primary feedback module (3) for outputting feedback voltage based on positive reference voltage and input voltage, wherein the overvoltage protection module (1) and the hysteresis comparison output module (2) are both electrically connected to the primary feedback module (3); The overvoltage protection module (1) includes an overvoltage protection unit (11), which includes a first Zener diode ZD1, a first resistor R1, a first capacitor C1, a second capacitor C2, and a first transistor Q1. One end of the first Zener diode ZD1, one end of the first capacitor C1, and the collector of the first transistor Q1 are all electrically connected to the positive input voltage VIN+. The other end of the first Zener diode ZD1, the other end of the first capacitor C1, and the base of the first transistor Q1 are all electrically connected to the negative input voltage VIN-, one end of the first resistor R1, and one end of the second capacitor C2. The emitter of the first transistor Q1, the other end of the first resistor R1, and the other end of the second capacitor C2 are connected. The circuit is connected by input voltages VIN+ and VIN- from the sensor terminals, and the input voltage range is 0 to 5V. Wherein, the first capacitor C1 and the second capacitor C2 are the inter-electrode filter capacitors of the first transistor Q1.

2. The control voltage conversion circuit based on an isolation transformer according to claim 1, characterized in that, The overvoltage protection module (1) further includes a low-pass filter unit (12), a bias voltage unit (13), and a rectifier bridge unit (14). The overvoltage protection unit (11) is electrically connected to the low-pass filter unit (12), the bias voltage unit (13), and the rectifier bridge unit (14) in sequence.

3. The control voltage conversion circuit based on an isolation transformer according to claim 2, characterized in that, The low-pass filter unit (12) includes a second resistor R2 and a third capacitor C3. One end of the second resistor R2 is electrically connected to the positive terminal of the input voltage VIN+, and the other end of the second resistor R2 is electrically connected to one end of the third capacitor C3. The other end of the third capacitor C3 is electrically connected to the emitter of the first transistor Q1.

4. The control voltage conversion circuit based on an isolation transformer according to claim 3, characterized in that, The bias voltage unit (13) includes a first diode D1 and a second diode D2. The negative terminal of the first diode D1 is connected to the common connection terminal of the second resistor R2 and the third capacitor C3. The positive terminal of the second diode D2 is connected to the common connection terminal of the third capacitor C3, the first transistor Q1, the first resistor R1 and the second capacitor C2.

5. The control voltage conversion circuit based on an isolation transformer according to claim 4, characterized in that, The rectifier bridge unit (14) includes a third diode D3, a fourth diode D4, a fifth diode D5, and a sixth diode D6. The negative terminals of the third diode D3 and the fifth diode D5 are both electrically connected to the positive terminal of the first diode D1. The positive terminal of the third diode D3 is electrically connected to the negative terminal of the fourth diode D4. The positive terminal of the fifth diode D5 is electrically connected to the negative terminal of the sixth diode D6. The positive terminals of the fourth diode D4 and the sixth diode D6 are both electrically connected to the negative terminal of the second diode D2.

6. The control voltage conversion circuit based on an isolation transformer according to any one of claims 1-5, characterized in that, The hysteresis comparator output module (2) includes a hysteresis comparator A1, a third resistor R3, a fourth resistor R4 and a fifth resistor R5. The sixth pin of the hysteresis comparator A1 is connected in series with the third resistor R3 and then connected to a pulse width modulation signal. The fifth pin of the hysteresis comparator A1 is connected in parallel with one end of the fourth resistor R4 and one end of the fifth resistor R5. The other end of the fourth resistor R4 is electrically connected to the frequency conversion voltage VF. The other end of the fifth resistor R5 is electrically connected to the seventh pin of the hysteresis comparator A1 and the primary feedback module (3).

7. The control voltage conversion circuit based on an isolation transformer according to claim 6, characterized in that, The primary feedback module (3) includes an isolation transformer T1, a sixth resistor R6, a seventh diode D7, a seventh resistor R7, an eighth resistor R8, a second Zener diode ZD2, and a fourth capacitor C4. The first and second pins of the isolation transformer T1 are connected to the overvoltage protection module (1). The third pin of the isolation transformer T1 is connected to the hysteresis comparator output module (2) and one end of the sixth resistor R6. The other end of the sixth resistor R6 is connected in series with the seventh diode D7 and then in parallel with one end of the second Zener diode ZD2, one end of the seventh resistor R7, and one end of the eighth resistor R8. The other end of the second Zener diode ZD2 is connected to the power supply VCC. The other end of the eighth resistor R8 is connected to the feedback voltage VO and one end of the fourth capacitor C4. The other end of the fourth capacitor C4, the other end of the seventh resistor R7, and the fourth pin of the isolation transformer T1 are all grounded.

8. The control voltage conversion circuit based on an isolation transformer according to claim 7, characterized in that, The second Zener diode, ZD2, is a clamping Zener diode.

9. An electrical appliance, characterized in that, It includes the control voltage conversion circuit based on the isolation transformer as described in any one of claims 1-8.

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