Constant-power high-frequency heating power supply control device

Abstract

The utility model discloses a constant-power high-frequency heating power supply control device. The device comprises an AC input terminal, a zero-cross detection module, a rectification filtering module, a PWM power control module, a voltage detection module, a first current detection module, a second current detection module, a processor control module and an output terminal. The rectifying and filtering module comprises a bridge type rectifying current and a filtering resistor and is used for converting alternating current voltage input through the input terminal into a direct current signal, and the capacitance value of the filtering capacitor does not exceed 1nF. The zero-crossing detection module is used for detecting a zero-crossing point of the AC power supply. The processor control module is used for sampling current and voltage signals output by the first current detection module, the second current detection module and the voltage detection module in each half alternating current period according to the zero crossing point information, calculating the output active power and adjusting the duty ratio of PWM waves according to the output power requirement so as to control the power of the heating power supply.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the field of electronic information technology, and relates to heating power control, in particular to a constant power high-frequency heating power control device. BACKGROUND

[0002] The power control circuit of the heating power device in the prior art is usually realized in two ways: one is to use thyristor to realize power control through phase shift regulation; and the other is to use MOS tube to realize power control through PWM regulation.

[0003] The prior art 1 (CN103987137A) proposes a circuit and method for controlling a metal ceramic heating body by using bidirectional thyristor, which controls the conduction or turn-off of the bidirectional thyristor through phase shift regulation to realize power control of the metal ceramic heating body. The disadvantage of this control method is that when the bidirectional thyristor is turned on at a high alternating voltage, the impact current value is very large, especially when the heating power is large, which will cause a strong impact on the power grid.

[0004] The prior art 2 (CN118889843A) discloses a power control method and device, heating power supply, computer equipment and storage medium, which controls the conduction time of the MOS tube through the method of PWM (pulse width modulation) to realize power control of the heating power supply. This method usually uses a rectifier bridge with a large-capacity filter capacitor to convert alternating voltage into direct current, resulting in that the input current and voltage are out of phase and the power factor is low. If a PFC circuit is used for power factor correction, on the one hand, the size and cost of the device are increased, and on the other hand, the effect is not ideal.

[0005] In addition, the sensitivity of the detection circuit in the prior art is limited, resulting in low power control accuracy and difficulty in maintaining the power stability of the heating circuit. UTILITY MODEL CONTENTS

[0006] In view of the deficiencies of the prior art, the utility model provides a constant power high-frequency heating power control device, a processor control module samples and detects the output voltage and current at a high sampling rate to improve the power detection accuracy and maintain the constant output power, a small-capacity filter capacitor is used to reduce the impact on the power grid, the power factor is high, and a PFC circuit is not needed, thereby reducing the manufacturing cost.

[0007] A constant power high-frequency heating power control device, comprising an alternating current input terminal, a zero-crossing detection module, a rectifier and filter module, a PWM power control module, a voltage detection module, a first current detection module, a second current detection module, a processor control module and an output terminal.

[0008] The two ends of the input terminal are connected with an alternating current power supply.

[0009] The input end of the zero-crossing detection module and the input end of the rectification filter module are connected with both ends of the input terminal. The zero-crossing detection module is used for detecting the zero-crossing point of the alternating power supply, and the output end thereof is connected with the zero-crossing detection input end of the processor control module. The rectification filter module converts the alternating voltage into a direct current signal through a bridge rectification circuit and a filter capacitor. The capacitance of the filter capacitor is not more than 0.1 nF.

[0010] The input end of the PWM power control module is connected with the output end of the rectification filter module, the output end thereof is connected with the output terminal, and the controlled end is connected with the power control end of the processor control module.

[0011] The input end of the first current detection module and the input end of the second current detection module are connected in series between the output end of the PWM power control module and the output terminal, and the output current and the abnormal working current of the PWM power control module are detected and sampled, respectively. The output end of the first current detection module and the output end of the second current detection module are connected with the output current detection end and the abnormal working current detection end of the processor control module, respectively.

[0012] The voltage detection module and the current detection module are connected in parallel, and are used for detecting and sampling the output voltage of the PWM power control module. The output end of the voltage detection module is connected with the voltage detection end of the processor control module.

[0013] The processor control module outputs a PWM wave to control the output power of the PWM power control module. The zero-crossing point of the alternating power supply output by the zero-crossing detection module is received, and the current and voltage signals output by the first current detection module, the second current detection module and the voltage detection module are sampled in each half of the alternating cycle, and the sampling frequency is above 100 kHz. The active power output by the PWM power control module is calculated, and the duty cycle of the PWM wave is adjusted according to the power demand of the heating power supply, so that the output power of the PWM power control module is consistent with the power demand of the heating power supply.

[0014] The utility model has the advantages of the following beneficial effects:

[0015] 1. The current detection circuit with narrow range is used for power control, and the current detection precision is improved.

[0016] 2. The voltage and current values are collected multiple times in one PWM cycle, the active power is directly calculated, the conversion of effective value is not needed, the operation amount is reduced, the controller cost is reduced, and the calculation result is more accurate.

[0017] 3. The filter capacitor with small capacitance is used, the power factor is high, the PFC circuit is not needed, and the current is continuous, and the impact on the power grid is small. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is a constant power high frequency heating power supply control device structure diagram.

[0019] Figure 2 It is a constant power high frequency heating power supply control device circuit principle diagram.

[0020] Figure 3 It is a zero-crossing detection waveform diagram.

[0021] Figure 4 It is a rectified and filtered waveform diagram.

[0022] Figure 5 It is a power PWM control function schematic diagram.

[0023] Figure 6 It is an output voltage and current sampling detection schematic diagram. DETAILED DESCRIPTION

[0024] The utility model is further explained and described below in combination with the drawings;

[0025] As Figure 1 shown, a constant power high frequency heating power supply control device includes an AC input terminal, a zero-crossing detection module, a rectification and filtering module, a PWM power control module, a voltage detection module, a first current detection module, a second current detection module, a processor control module and an output terminal.

[0026] As Figure 2 shown, the two ends of the input terminal are connected with an AC power source.

[0027] The zero-crossing detection module is connected with the two ends of the input terminal and is used for detecting the zero-crossing point of the AC power source and includes an operational amplifier chip U2 and resistors R5-R8, wherein one end of each of the resistors R5 and R7 is connected with one end of the input terminal, and the other end of each of the resistors R5 and R7 is connected with the non-inverting input terminal and the inverting input terminal of the operational amplifier chip U2 respectively. One end of the resistor R6 is grounded, and the other end of the resistor R6 is connected with the non-inverting input terminal of the operational amplifier chip U2. The two ends of the resistor R8 are connected with the inverting input terminal and the output terminal of the operational amplifier chip U2 respectively. The output terminal of the operational amplifier chip U2 is connected with the zero-crossing detection input terminal of the processor control module, as Figure 3 shown, there are two zero-crossing points in each AC cycle, and T0 is half of an AC cycle.

[0028] The input end of the rectification and filtering module is connected with the two ends of the input terminal, and the AC voltage power source is converted into a DC signal through a bridge rectifier circuit D1 and a filter capacitor C1. In the embodiment, the capacitance value of the filter capacitor C1 is 0.1 nF, and the voltage signal waveform after the rectification and filtering module is as Figure 4Compared with the prior art that rectifies the voltage signal into a "straight line" type by a large filter capacitor, the filter capacitor C1 in the application has a small capacitance value, so the rectified and filtered voltage signal is not equal everywhere in a half cycle, but can make the input current continuous and in phase with the input voltage, improve the power factor of the power supply, and reduce the current impact on the power grid.

[0029] The PWM power control module includes a switch tube Q1, an inductor L1, and a diode D2. The controlled end of the switch tube Q1 is connected to the power control end of the processor control module, the input end is connected to the output end of the rectification and filtering module, and the output end is connected to one end of the inductor L1. The other end of the inductor L1 is connected to the positive end of the output terminal and the negative electrode of the diode D2, and the positive electrode of the diode D2 is grounded.

[0030] The input ends of the first current detection module and the second current detection module are connected in series between the output terminal and the ground, and detect and sample the output current and the abnormal working current of the PWM power control module, respectively. The output ends are connected to the output current detection end and the abnormal working current detection end of the processor control module. The first current detection module and the second current detection module have the same structure. The first current detection module includes a sampling resistor R11, an input resistor R12, a feedback resistor R13, and an operational amplifier chip U11. The second current detection module includes a sampling resistor R21, an input resistor R22, a feedback resistor R23, and an operational amplifier chip U12. The sampling resistors R11 and R21 are connected in series between the ground and the output terminal, and the end close to the output terminal is connected to the non-inverting input end of the operational amplifier chip U11 and U12, respectively. The end close to the ground is connected to one end of the input resistors R12 and R22, respectively. The other ends of the input resistors R12 and R22 are connected to the inverting input end of the operational amplifier chip U11 and U12, respectively. The feedback resistors R13 and R23 are connected to the inverting input end and the output end of the operational amplifier chip U11 and U12, respectively. The output ends of the operational amplifier chips U11 and U12 are connected to the output current detection end and the abnormal working current detection end of the processor control module, respectively. The output voltage 、 are respectively:

[0031]

[0032]

[0033] wherein, represents the sampled output current, represents the sampled abnormal working current.

[0034] The normal working current value variation range is relatively small, a larger current gain is adopted, a larger current signal can be obtained, the current detection precision is improved, and the power calculation precision is improved. In the embodiment, the resistance values of the sampling resistor R11, the input resistor R12 and the feedback resistor R13 of the first current detection module are respectively 0.05Ω, 1kΩ and 10kΩ, and the gain of the amplifier in the first current detection module is 0.5V / A. Therefore, under the maximum normal working current, the output voltage of the operational amplifier chip U11 does not exceed the reference voltage of the controller.

[0035] In the abnormal condition, the current value range becomes very wide, and in this case, current protection needs to be performed. If the current gain is too large, the amplifier output will be saturated, causing signal distortion, so a smaller current gain needs to be selected. In the second current detection module, the resistance values of the sampling resistor R21, the input resistor R22 and the feedback resistor R23 are respectively 0.005Ω, 1kΩ and 4.7kΩ, and the gain of the amplifier is 0.0235V / A. Therefore, under the abnormal condition, the output voltage of the operational amplifier chip U12 does not exceed the reference voltage of the controller.

[0036] The voltage detection module is connected to the output terminal, and is used for detecting and sampling the output voltage of the PWM power control module. The voltage detection module includes an operational amplifier chip U1 and resistors R1 to R4. The two ends of the resistor R1 are respectively connected to one end of the output terminal and the non-inverting input terminal of the operational amplifier chip U1. The two ends of the resistor R2 are respectively connected to the ground and the non-inverting input terminal of the operational amplifier chip U1. The two ends of the resistor R3 are respectively connected to the other end of the output terminal and the inverting input terminal of the operational amplifier chip U1. The two ends of the resistor R4 are respectively connected to the inverting input terminal of the operational amplifier chip U1 and the output terminal. The output terminal of the operational amplifier chip U1 is connected to the voltage detection terminal of the processor control module.

[0037] As shown in FIG. 4, in each half of the alternating current cycle, the processor control module simultaneously samples the output voltage and the current, the voltage and the current have the same phase, and the power calculation precision is improved. According to the power calculation result, the PWM control duty cycle is adjusted, so that the output power reaches the set value. Figure 5

[0038] The frequency of the heating power supply is controlled by using the control device, and the specific steps are as follows:

[0039] Step 1: The zero-crossing point of the alternating current power supply is detected by the zero-crossing detection module, and the half cycle T0 of the alternating current power supply is obtained.

[0040] Step 2: The PWM control module is turned on and off by the PWM control module. As shown in FIG. 5, in each half of the alternating current cycle, the processor control module simultaneously samples the output voltage and the current, the voltage and the current have the same phase, and the power calculation precision is improved. According to the power calculation result, the PWM control duty cycle is adjusted, so that the output power reaches the set value. Figure 6 ​As shown, during one PWM active level, the output voltage, output current and abnormal working current are sampled for multiple times. In this example, the sampling frequency is 400 kHz. The multiple sampling data makes the detected output voltage and current value curve more consistent with the actual output voltage and current curve, reducing the error.

[0041] Step 3, calculate the active power according to the sampled output voltage and output current data:

[0042]

[0043] wherein k represents the sampling number within half cycle T0, , respectively represent the sampled output voltage, output current.

[0044] Step 4, compare the active power calculated in step 3 with the predetermined power of the heating power supply When > , decrease the PWM duty cycle, when , increase the PWM duty cycle, so as to make = . The PWM adjustment formula is:

[0045]

[0046] wherein and are adjustment coefficients.

[0047] Step 5, compare the sampled abnormal working current with the set threshold When > , output low level, turn off the PWM power control module. In this embodiment, the threshold is set as 20 A.

Claims

1. A constant power high-frequency heating power supply control device, comprising AC input terminals, zero-crossing detection module, rectification filtering module, PWM power control module, processor control module and output terminals, the two ends of the input terminals are connected with AC power supply, the input ends of the zero-crossing detection module and the rectification filtering module are connected with the two ends of the input terminals; the zero-crossing detection module is used for detecting the zero-crossing point of the AC power supply, and the output end thereof is connected with the zero-crossing detection input end of the processor control module; the rectification filtering module converts AC voltage into DC signal through a bridge rectifier circuit and a filtering capacitor; the input end of the PWM power control module is connected with the output end of the rectification filtering module, the output end thereof is connected with the output terminals, and the controlled end is connected with the power control end of the processor control module; the processor control module receives the zero-crossing point position of the AC power supply output by the zero-crossing detection module, outputs PWM wave, and controls the output power of the PWM power control module; characterized in that: The voltage detection module, the first current detection module and the second current detection module are further included. The input ends of the first current detection module and the second current detection module are connected in series between the output end of the PWM power control module and the output terminal, and the output currents and the abnormal working currents of the PWM power control module are detected and sampled, respectively, and the output ends are connected to the output current detection end and the abnormal working current detection end of the processor control module, respectively. The voltage detection module and the current detection module are connected in parallel, and the output voltage of the PWM power control module is detected and sampled, and the output end is connected to the voltage detection end of the processor control module. The processor control module samples the current and voltage signals output by the first current detection module, the second current detection module and the voltage detection module in each half of the alternating current cycle, and the sampling frequency is above 100 kHz; the active power output by the PWM power control module is calculated, and the duty cycle of the PWM wave is adjusted according to the power requirement of the heating power supply, so that the output power of the PWM power control module is consistent with the power requirement of the heating power supply. In the rectification and filtering module, the capacitance of the filtering capacitor is not more than 0.1 nF.

2. The control device for a constant-power high-frequency heating power source according to claim 1, characterized by: The zero-crossing detection module includes an operational amplifier chip U2 and resistors R5-R8, wherein one end of each of the resistors R5 and R7 is connected to one end of the input terminal, and the other end of each of the resistors R5 and R7 is connected to the non-inverting input end and the inverting input end of the operational amplifier chip U2, respectively; one end of the resistor R6 is grounded, and the other end of the resistor R6 is connected to the non-inverting input end of the operational amplifier chip U2; the two ends of the resistor R8 are connected to the inverting input end and the output end of the operational amplifier chip U2, respectively; and the output end of the operational amplifier chip U2 is connected to the zero-crossing detection input end of the processor control module.

3. The control device for a constant power high frequency heating power supply as recited in claim 1, wherein: The PWM power control module includes a switching tube Q1, an inductor L1 and a diode D2; wherein the controlled end of the switching tube Q1 is connected to the power control end of the processor control module, the input end is connected to the output end of the rectification and filtering module, and the output end is connected to one end of the inductor L1; the other end of the inductor L1 is connected to the positive end of the output terminal and the negative electrode of the diode D2, and the positive electrode of the diode D2 is grounded.

4. The control device for a constant power high frequency heating power supply as recited in claim 1, wherein: The first current detection module includes a sampling resistor R11, an input resistor R12, a feedback resistor R13 and an operational amplifier chip U11; the second current detection module includes a sampling resistor R21, an input resistor R22, a feedback resistor R23 and an operational amplifier chip U12; the sampling resistors R11 and R21 are connected in series between the ground and the output terminal, and one end close to the output terminal is connected to the non-inverting input end of the operational amplifier chip U11 and U12, respectively; one end close to the ground is connected to one end of the input resistors R12 and R22, respectively; the other end of the input resistors R12 and R22 is connected to the inverting input end of the operational amplifier chip U11 and U12, respectively; the two ends of the feedback resistors R13 and R23 are connected to the inverting input end and the output end of the operational amplifier chip U11 and U12, respectively; and the output ends of the operational amplifier chips U11 and U12 are connected to the output current detection end and the abnormal working current detection end of the processor control module, respectively.

5. The control apparatus for a constant power high frequency heating power supply as recited in claim 4, wherein: The amplifier gain in the first current detection module is greater than the amplifier gain in the second current detection module.

6. A constant power high frequency heating power supply control device as claimed in claim 4 or 5, characterized in that: The gain of the amplifier in the first current detection module is 0.5V / A, and the gain of the amplifier in the second current detection module is 0.025V / A.

7. The control device for a constant power high frequency heating power supply as claimed in claim 4 or 5, characterized by: In the first current detection module, the resistance values of the sampling resistor R11, the input resistor R12 and the feedback resistor R13 are respectively 0.05Ω, 1kΩ and 10kΩ; in the second current detection module, the resistance values of the sampling resistor R21, the input resistor R22 and the feedback resistor R23 are respectively 0.005Ω, 1kΩ and 4.7kΩ.

8. The control device for a constant power high frequency heating power supply as recited in claim 1, wherein: The voltage detection module comprises an operational amplifier chip U1 and resistors R1-R4, wherein the two ends of the resistor R1 are respectively connected with one end of an output terminal and a non-inverting input terminal of the operational amplifier chip U1, and the two ends of the resistor R2 are respectively connected with the ground and the non-inverting input terminal of the operational amplifier chip U1; the two ends of the resistor R3 are respectively connected with the other end of the output terminal and an inverting input terminal of the operational amplifier chip U1, and the two ends of the resistor R4 are respectively connected with the inverting input terminal of the operational amplifier chip U1 and an output terminal; and the output terminal of the operational amplifier chip U1 is connected with a voltage detection terminal of a processor control module.

Images