Alternating voltage isolation detection circuit

Abstract

The utility model relates to an AC voltage isolation detection circuit, comprising a peak voltage holding module, a voltage conversion module, a voltage calibration module and a voltage detection module, the peak voltage holding module is connected with the voltage conversion module, and the voltage calibration module is connected with the voltage detection module. The voltage calibration module is connected between the peak voltage holding module and the voltage conversion module, and the voltage detection module is connected with the voltage calibration module and the voltage conversion module. Compared with the prior art, the utility model has the advantages of cost and precision and the like.

Description

Technical Field

[0001] The utility model relates to a voltage detection circuit, in particular to an AC voltage isolation detection circuit. Background Art

[0002] Currently, a single-chip microcomputer or professional power detection chip is commonly used to convert the detected AC voltage into a digital signal, which is then transmitted to the secondary-side MCU for analysis via a high-speed optocoupler using a certain communication protocol (commonly I2C). However, this existing solution has problems such as high cost.

[0003] The existing voltage detection circuit includes a peak voltage holding module and a voltage conversion module. The principle of this voltage detection circuit is not complicated, but its practicality is not strong due to its low precision. There are three main factors affecting its precision:

[0004] First: The conversion chip accuracy is not high

[0005] Since the three-in-one dimming IC makes a fixed linear correspondence between the input voltage and the PWM duty cycle, the accuracy of the IC's own voltage corresponding to the PWM duty cycle is low.

[0006] Second: Signal distortion of low-speed optocoupler

[0007] Because high-speed optocouplers are expensive, this solution uses low-speed optocouplers. However, ordinary low-speed optocouplers have turn-on delay and turn-off tailing, which makes the PWM duty cycle detection very inaccurate, thus reducing the accuracy of the detected voltage V.

[0008] Third: Temperature influence

[0009] The temperature characteristics of the IC, the effects of high and low temperatures, the corresponding relationship between the voltage and PWM duty cycle of the dimming IC, the CTR of the optocoupler, etc., are all closely related to its operating temperature. Utility Model Content

[0010] The purpose of the present invention is to overcome the defects of the prior art and provide an AC voltage isolation detection circuit that takes both cost and accuracy into consideration.

[0011] The purpose of the utility model can be achieved through the following technical solutions:

[0012] According to one aspect of the present utility model, an AC voltage isolation detection circuit is provided, comprising a peak voltage holding module and a voltage conversion module, wherein the peak voltage holding module is connected to the voltage conversion module. The detection circuit further comprises a voltage calibration module and a voltage detection module, wherein the voltage calibration module is connected between the peak voltage holding module and the voltage conversion module, and the voltage detection module is respectively connected to the voltage calibration module and the voltage conversion module.

[0013] As a preferred technical solution, the peak voltage maintenance module includes a rectifier unit BD1, a filter capacitor C1, an isolation diode D1 and a filter capacitor C2. The input end of the rectifier unit BD1 is connected to the AC input voltage, and the positive pole of the output end is respectively connected to one end of the filter capacitor C1 and the positive pole of the isolation diode D1. The negative pole of the isolation diode D1 is respectively connected to the voltage conversion module and one end of the filter capacitor C2. The negative pole of the output end of the rectifier unit BD1 is respectively connected to the other end of the filter capacitor C1, the other end of the filter capacitor C2 and the voltage calibration module.

[0014] As a preferred technical solution, the voltage conversion module includes a three-in-one dimming chip IC1, a photocoupler PC1, resistors R1, R4, R6, R8, R10 and a diode D3;

[0015] The cathode of the isolation diode D1 is connected to the anode of the diode D3 after passing through resistors R1, R4, and R6 in sequence. The cathode of the diode D3 is connected to one end of the resistor R8, the three-in-one dimming chip IC1, and one end of the resistor R10 respectively. The other end of the resistor R8 is connected to the reference voltage end, and the other end of the resistor R10 is grounded. The three-in-one dimming chip IC1 is connected to the light-emitting diode PC1A of the photoelectric coupler PC1.

[0016] As a preferred technical solution, the three-in-one dimming chip IC1 is connected to the light-emitting diode of the photocoupler PC1 through the resistor R7.

[0017] As a preferred technical solution, the voltage calibration module includes a photocoupler PC2, a MOS transistor Q1, a MOS transistor Q2, a capacitor C3 and a resistor R12. The gate of the MOS transistor Q1 is respectively connected to the emitter of the transistor PC2B of the photocoupler PC2 and one end of the resistor R12. The drain of the MOS transistor Q1 is connected to the positive electrode of the diode D3. The other end of the resistor R12 is respectively connected to one end of the capacitor C3 and the gate of the MOS transistor Q2. The drain of the MOS transistor Q2 is connected to one end of the resistor R8. The other end of the capacitor C3, the source of the MOS transistor Q1, and the source of the MOS transistor Q2 are all grounded.

[0018] As a preferred technical solution, the collector of the transistor PC2B of the photoelectric coupler PC2 is connected to the reference voltage terminal through the resistor R5.

[0019] As a preferred technical solution, the emitter of the transistor PC2B of the photoelectric coupler PC2 is grounded via a resistor R11.

[0020] As a preferred technical solution, the drain of the MOS tube Q2 is connected to one end of the resistor R8 through the resistor R14.

[0021] As a preferred technical solution, the voltage detection module includes a three-in-one dimming chip IC2, and the three-in-one dimming chip IC2 is respectively connected to the transistor PC1B of the photocoupler PC1 and the light-emitting diode PC2A of the photocoupler PC2.

[0022] As a preferred technical solution, the three-in-one dimming chip IC2 is connected to the emitter of the transistor PC1B of the photocoupler PC1 through the resistor R2, and the three-in-one dimming chip IC2 is connected to the positive electrode of the light-emitting diode PC2A of the photocoupler PC2 through the resistor R3.

[0023] Compared with the prior art, the utility model has the following advantages:

[0024] 1) The present invention is low-cost. After the AC voltage and the reference voltage are accumulated, the DC voltage is converted into PWM through a low-cost three-in-one dimming IC, and the PWM signal is then transmitted to the secondary side through a low-speed optocoupler. Since the temperature characteristics, light attenuation, and consistency of the low-speed optocoupler will affect the accuracy of voltage detection, the present invention adds another low-speed optocoupler for calibration. Calibration work is performed before the input voltage needs to be detected.

[0025] 2) The peak voltage holding module of the utility model converts AC voltage into DC voltage and also quickly responds to changes in input voltage, thereby achieving real-time and effective detection of input voltage;

[0026] 3) When the present invention detects the input AC voltage V, the optocoupler PC2 is turned off, and the duty cycle detected by the chip is deducted from the accumulated error to accurately detect the input voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a specific circuit diagram of the utility model;

[0028] Figure 2 This is a specific circuit diagram of the voltage detection module of the utility model. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0030] like Figure 1 and Figure 2As shown, an AC voltage isolation detection circuit includes a peak voltage holding module and a voltage conversion module, wherein the peak voltage holding module is connected to the voltage conversion module. It is characterized in that the detection circuit also includes a voltage calibration module and a voltage detection module, wherein the voltage calibration module is connected between the peak voltage holding module and the voltage conversion module, and the voltage detection module is respectively connected to the voltage calibration module and the voltage conversion module.

[0031] like Figure 1 As shown, the peak voltage holding module includes a rectifier unit BD1, a filter capacitor C1, an isolation diode D1 and a filter capacitor C2. The input end of the rectifier unit BD1 is connected to the AC input voltage, and the positive electrode of the output end is respectively connected to one end of the filter capacitor C1 and the positive electrode of the isolation diode D1. The cathode of the isolation diode D1 is respectively connected to the voltage conversion module and one end of the filter capacitor C2. The negative electrode of the output end of the rectifier unit BD1 is respectively connected to the other end of the filter capacitor C1, the other end of the filter capacitor C2 and the voltage calibration module.

[0032] The peak voltage hold module operates as follows: the AC input voltage is rectified by BD1 and filtered by C1 into a DC pulsating waveform. Peak voltage is then maintained using isolation diode D1 and filter capacitor C2. Because the low-cost three-in-one dimming IC1 can only convert DC voltage into a PWM output, it is necessary to convert the AC voltage to DC while also requiring a fast response to input voltage changes to effectively detect the input voltage in real time.

[0033] like Figure 1 As shown, the voltage conversion module includes a three-in-one dimming chip IC1, a photocoupler PC1, resistors R1, R4, R6, R8, R10, and a diode D3. The cathode of the isolation diode D1 is connected to the anode of the diode D3 through resistors R1, R4, and R6 in sequence. The cathode of the diode D3 is connected to one end of the resistor R8, the three-in-one dimming chip IC1, and one end of the resistor R10. The other end of the resistor R8 is connected to the reference voltage terminal, and the other end of the resistor R10 is grounded. The three-in-one dimming chip IC1 is connected to the light-emitting diode PC1A of the photocoupler PC1. The three-in-one dimming chip IC1 is connected to the light-emitting diode of the photocoupler PC1 through a resistor R7.

[0034] The specific working process of the voltage conversion module is as follows: the previous AC peak holding voltage V1 is divided by resistors R1\R4\R6 in series with diodes D3 and R10 to obtain a voltage V2. The other voltage VREF (10V) is divided by R8 and R10, and the voltage V3 divided on R10 is converted into the accumulated value of V2+V3. The signal is transmitted to the secondary side MCU through the optocoupler PC1. Because VREF is a fixed reference voltage of 10V, the DC voltage of V1 is easy to calculate. The DC voltage of V1 and the input AC voltage are in the square root of 2 relationship in the case of a sine wave, so the effective value of the input voltage V can be detected.

[0035] like Figure 1 As shown, the voltage calibration module includes a photocoupler PC2, a MOS transistor Q1, a MOS transistor Q2, a capacitor C3, and a resistor R12. The gate of the MOS transistor Q1 is connected to the emitter of the transistor PC2B of the photocoupler PC2 and one end of the resistor R12. The drain of the MOS transistor Q1 is connected to the anode of the diode D3. The other end of the resistor R12 is connected to one end of the capacitor C3 and the gate of the MOS transistor Q2. The drain of the MOS transistor Q2 is connected to one end of the resistor R8. The other end of the capacitor C3, the source of the MOS transistor Q1, and the source of the MOS transistor Q2 are all grounded. The collector of the transistor PC2B of the photocoupler PC2 is connected to the reference voltage terminal via resistor R5. The emitter of the transistor PC2B of the photocoupler PC2 is grounded via resistor R11. The drain of the MOS transistor Q2 is connected to one end of the resistor R8 via resistor R14.

[0036] This utility model also incorporates a calibration circuit. Before each test, the secondary-side MCU sends a signal to turn on the optocoupler PC2. Initially, PC2 turns on, turning on MOS transistor Q1. This results in the input voltage to the three-in-one dimming IC being only V3.1, which is the voltage divided by R8 and R10, VREF. This is the input voltage V3.1 corresponding to the PWM duty cycle detected by the MCU. After PC2 turns on for a certain period of time (depending on the τ value of R12 and C3), MOS transistor Q2 also turns on. R14 and R10, connected in parallel, divide VREF with R8 to obtain V3.2, which is the input voltage V3.2 corresponding to the PWM duty cycle detected by the MCU. Given that V3.1 and V3.2 are both known voltages (VREF 10V, R8, R10, and R14 are known), two different duty cycles corresponding to two different input voltages to IC1 can be determined, thus identifying any accumulated errors in the system. When we need to detect the input AC voltage V, we turn off the optocoupler PC2. The duty cycle detected by the MCU is deducted from the above accumulated error to accurately detect the input voltage.

[0037] like Figure 2As shown, the voltage detection module includes a three-in-one dimming chip IC2, which is connected to the transistor PC1B of the photocoupler PC1 and the light-emitting diode PC2A of the photocoupler PC2. The three-in-one dimming chip IC2 is connected to the emitter of the transistor PC1B of the photocoupler PC1 through a resistor R2, and the three-in-one dimming chip IC2 is connected to the positive electrode of the light-emitting diode PC2A of the photocoupler PC2 through a resistor R3.

[0038] The MCU processes IC2, receives the PWM duty cycle signal through PC1 and R2, and performs calibration through PC2 and R3.

[0039] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. An AC voltage isolation detection circuit, comprising a peak voltage holding module and a voltage conversion module, wherein the peak voltage holding module is connected to the voltage conversion module, characterized in that: The detection circuit further includes a voltage calibration module and a voltage detection module. The voltage calibration module is connected between the peak voltage holding module and the voltage conversion module. The voltage detection module is connected to the voltage calibration module and the voltage conversion module respectively.

2. The AC voltage isolation detection circuit according to claim 1, characterized in that: The peak voltage holding module includes a rectifier unit BD1, a filter capacitor C1, an isolation diode D1 and a filter capacitor C2. The input end of the rectifier unit BD1 is connected to the AC input voltage, and the positive electrode of the output end is respectively connected to one end of the filter capacitor C1 and the positive electrode of the isolation diode D1. The cathode of the isolation diode D1 is respectively connected to the voltage conversion module and one end of the filter capacitor C2. The negative electrode of the output end of the rectifier unit BD1 is respectively connected to the other end of the filter capacitor C1, the other end of the filter capacitor C2 and the voltage calibration module.

3. The AC voltage isolation detection circuit according to claim 2, characterized in that: The voltage conversion module includes a three-in-one dimming chip IC1, a photoelectric coupler PC1, resistors R1, R4, R6, R8, R10 and a diode D3; The cathode of the isolation diode D1 is connected to the anode of the diode D3 after passing through resistors R1, R4, and R6 in sequence. The cathode of the diode D3 is connected to one end of the resistor R8, the three-in-one dimming chip IC1, and one end of the resistor R10 respectively. The other end of the resistor R8 is connected to the reference voltage end, and the other end of the resistor R10 is grounded. The three-in-one dimming chip IC1 is connected to the light-emitting diode PC1A of the photoelectric coupler PC1.

4. The AC voltage isolation detection circuit according to claim 3, characterized in that: The three-in-one dimming chip IC1 is connected to the light-emitting diode of the photocoupler PC1 through the resistor R7.

5. The AC voltage isolation detection circuit according to claim 3, characterized in that: The voltage calibration module includes a photoelectric coupler PC2, a MOS transistor Q1, a MOS transistor Q2, a capacitor C3, and a resistor R12. The gate of the MOS transistor Q1 is respectively connected to the emitter of the transistor PC2B of the photoelectric coupler PC2 and one end of the resistor R12. The drain of the MOS transistor Q1 is connected to the anode of the diode D3. The other end of the resistor R12 is respectively connected to one end of the capacitor C3 and the gate of the MOS transistor Q2. The drain of the MOS transistor Q2 is connected to one end of the resistor R8. The other end of the capacitor C3, the source of the MOS transistor Q1, and the source of the MOS transistor Q2 are all grounded.

6. The AC voltage isolation detection circuit according to claim 5, characterized in that: The collector of the transistor PC2B of the photoelectric coupler PC2 is connected to the reference voltage terminal through the resistor R5.

7. The AC voltage isolation detection circuit according to claim 5, characterized in that: The emitter of the transistor PC2B of the photoelectric coupler PC2 is grounded via a resistor R11.

8. The AC voltage isolation detection circuit according to claim 5, characterized in that: The drain of the MOS tube Q2 is connected to one end of the resistor R8 through the resistor R14.

9. The AC voltage isolation detection circuit according to claim 5, characterized in that: The voltage detection module includes a three-in-one dimming chip IC2 , and the three-in-one dimming chip IC2 is connected to the transistor PC1B of the photoelectric coupler PC1 and the light-emitting diode PC2A of the photoelectric coupler PC2 .

10. The AC voltage isolation detection circuit according to claim 9, characterized in that: The three-in-one dimming chip IC2 is connected to the emitter of the transistor PC1B of the photocoupler PC1 through the resistor R2, and the three-in-one dimming chip IC2 is connected to the positive electrode of the light-emitting diode PC2A of the photocoupler PC2 through the resistor R3.

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