Power supply voltage generating circuit of microwave oven inverter

Abstract

The utility model provides a power supply voltage generating circuit of a microwave oven inverter, which comprises a power supply voltage generating unit, a power semiconductor used for the function of the inverter, a high-voltage transformer used for generating high voltage through the function of the inverter, and a magnetron used for transmitting microwave waves through the high-voltage transformer, wherein the power supply voltage generation unit is composed of a first power supply voltage generation unit and a second power supply voltage generation unit; the power supply voltage required by the inverter control unit is generated by a first power supply voltage generator and a second power supply voltage generator, and when the first power supply voltage generator is stopped, the second power supply voltage generator generates the power supply voltage by performing back-voltage rectification on the collector AC output of the power semiconductor. And the power supply voltage is supplied to the inverter control part, so that the power supply voltage is used as a power supply voltage supply source after the first power supply voltage generation part stops running, no heat is generated in the current-limiting resistor, and the energy efficiency of the microwave oven inverter is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of microwave ovens, in particular to a power supply voltage generating circuit of a microwave oven inverter. Background Art

[0002] In the circuit of the existing microwave inverter, there is a forward conversion diode that receives the commercial AC power supply and converts it into DC, a reactor is connected to the positive (+) terminal of the forward conversion diode, and a smoothing capacitor is connected to the other end of the reactor. In addition, a rectifier diode is connected to the commercial AC power supply, the output end of the rectifier diode and is connected to a current limiting resistor, the other end of the current limiting resistor is connected to a constant voltage diode and a smoothing capacitor, and is converted into a predetermined amount of constant voltage, which is then used as a power supply voltage VCC of the inverter control unit.

[0003] However, in the process of generating the power supply voltage VCC, the energy efficiency of the existing microwave oven inverter is reduced due to the energy of the heat generated by the current limiting resistor itself. Summary of the invention

[0004] In view of the defects existing in the prior art, the purpose of the utility model is to provide a power supply voltage generating circuit for a microwave oven inverter, so as to solve the problem that the energy efficiency of the inverter is reduced due to the energy of the heat generated by the current limiting resistor itself during the process of generating the power supply voltage VCC of the microwave oven inverter.

[0005] In order to achieve the above purpose, the technical solution adopted by the utility model is as follows:

[0006] The present application provides a power supply voltage generating circuit for a microwave oven inverter, the power supply voltage generating circuit comprising a power supply voltage generating unit for supplying power supply voltage to an inverter control unit, a power semiconductor for inverter action, a high voltage transformer for generating high voltage through inverter action, and a magnetron for emitting microwave waves through the high voltage transformer, wherein the power supply voltage generating unit is composed of a first power supply voltage generating unit and a second power supply voltage generating unit.

[0007] Furthermore, the first power supply voltage generating unit includes a current limiting resistor, a transistor, a base resistor and a base capacitor, one end of the current limiting resistor is electrically connected to the collector of the transistor, the base resistor is electrically connected to the base of the transistor through the base capacitor, and the emitter of the transistor is electrically connected to the inverter control unit.

[0008] Furthermore, the first power supply voltage generating unit further includes a constant voltage diode, and the constant voltage diode is connected between the emitter and the base resistor of the transistor.

[0009] Furthermore, the second power supply voltage generating unit includes a capacitor, a first rectifier diode and a second rectifier diode, one end of the capacitor is electrically connected to the primary coil of the high-voltage transformer, and the other end of the capacitor is electrically connected to the positive electrode of the first rectifier diode and the negative electrode of the second rectifier diode, respectively.

[0010] Furthermore, the cathode of the first rectifier diode is electrically connected to a constant voltage diode and a smoothing capacitor.

[0011] The beneficial effects of the utility model are as follows: the power supply voltage required by the inverter control unit is generated by the first power supply voltage generator and the second power supply voltage generator. When the first power supply voltage generator stops running, the second power supply voltage generator performs back-voltage rectification on the collector AC output of the power semiconductor to generate the power supply voltage, and provides the power supply voltage to the inverter control unit, thereby serving as the power supply voltage supply source after the first power supply voltage generator stops running. No heat is generated in the current limiting resistor, thereby improving the energy efficiency of the microwave oven inverter. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 4 is a circuit diagram of a power supply voltage generating circuit of a microwave oven inverter in an embodiment of the present application. DETAILED DESCRIPTION

[0013] The utility model is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0014] See attached Figure 1 As shown, the present embodiment provides a power supply voltage generating circuit for a microwave oven inverter, which is provided with a forward conversion diode 1 that receives a commercial AC power supply and converts it into DC, a reactor 2 is connected to the positive (+) terminal of the forward conversion diode 1, and a smoothing capacitor 3 is connected to the other end of the reactor 2. In addition, rectifier diodes 7 and 8 are connected to the commercial AC power supply, and the output ends of the rectifier diodes 7 and 8 are connected to a current limiting resistor 9, and the other end of the current limiting resistor 9 is connected to a constant voltage diode 5 and a smoothing capacitor 4, and is converted into a predetermined amount of constant voltage, and then used as a power supply voltage VCC of an inverter control unit 6.

[0015] The inverter control unit 6 generates a gate pulse Q for driving the power semiconductor 11, and continuously applies the gate pulse Q to the gate G of the power semiconductor 11. When the gate power Q is high, the collector C and the emitter E of the power semiconductor 11 are turned on, so that current flows through the primary coil 21 of the high-voltage transformer 20. When the gate power Q is low, the collector C and the emitter E of the power semiconductor 11 are cut off, and the current in the primary coil 21 of the high-voltage transformer 20 flows in the direction opposite to the direction of the primary coil 21 by the back electromotive force. The structure of the high-voltage transformer 20 is divided into a primary coil 21 and secondary coils 22 and 23, and the secondary coil is further divided into a high-voltage coil 22 and a filament coil 23. When an AC high voltage is induced in the high-voltage coil 22 by the action of the inverter on the primary coil 21 side, the high-voltage rectifying unit 12 performs back voltage rectification on the AC high voltage and applies the back voltage rectification to the negative pole 13 of the magnetron 14. The magnetron is equivalent to a two-pole vacuum tube, and in order to make the vacuum tube work, the filament must be heated. The filament coil 23 of the high-voltage transformer 20 is connected to the filament of the magnetron 14 to heat the filament.

[0016] In the present embodiment, the power supply voltage generating circuit of the microwave oven inverter is composed of a first power supply voltage generating section 30 and a second power supply voltage generating section 40. Such a first power supply voltage generating section 30 and a second power supply voltage generating section 40 are constituted by a power supply voltage generating unit for supplying power supply voltage to an inverter control section. The first power supply voltage generator 30 supplies the power supply voltage VCC only for the first few seconds after power is supplied to realize the inverter action through the output semiconductor 11, and then stops the operation immediately, after which the second power supply voltage generator 40 is responsible for supplying the power supply voltage VCC. That is, since the first power supply voltage generator 30 is turned off after operating for a few seconds only when power is re-input, during the subsequent normal operation, current does not flow through the current limiting resistor 31, so that heat is not generated in the current limiting resistor 31. The operation of each unit of the microwave inverter circuit according to the embodiment will be described below. For convenience, it is assumed that the rated voltage of the constant voltage diode 35 is 15V, because when power is applied, the base capacitor 34 is in a short-circuit state, so the base bias current generated by the base resistor 33 flows to the base B of the transistor 32. In this way, the collector C and emitter E of the transistor 32 are turned on, and the voltage attenuated by the current limiting resistor 31 is applied to the constant voltage diode 5 and the smoothing capacitor 4, thereby forming a power supply voltage VCC of +15V. As time goes by, the base capacitor 34 gradually starts to charge and is fully charged, and the current flowing to the base B of the transistor 32 through the base capacitor 34 no longer flows, the transistor 32 is cut off, and the current flowing from the collector C of the transistor 32 to the emitter E is cut off.

[0017] The time for the transistor to switch from the on state to the off state is only a few seconds, and the factor determining this time is the RC time constant between the resistor 33 and the base capacitor 34, and the constant voltage diode 35 keeps the voltage applied across the base capacitor 34 within the rated value of the base capacitor 34, thereby protecting the base capacitor 34. When the transistor 32 is cut off, the power supply voltage VCC disappears, causing the inverter to stop operating, but since there is the second power supply voltage generator 40, after the first power supply voltage generator 30 stops generating the power supply voltage VCC, the inverter control unit 6 continues to operate using the power supply voltage VCC generated by the second power supply voltage generator 40.

[0018] The components of the second power supply voltage generating unit 40 are back-voltage rectifiers, which are well-known technologies. Therefore, the following is a brief description: The AC voltage generated in the collector C of the output semiconductor 11 is attenuated by the coupling capacitor 41 and applied to the rectifying diodes 42 and 43. The frequency of the AC waveform generated on the collector C of the output semiconductor 11 is about 20Khz to 30Khz, and the voltage is a high level of about 1000V. Therefore, it is impossible to form a power supply voltage VCC of about 15V, so it is necessary to attenuate it by the coupling capacitor 41. When the voltage applied to the rectifying diodes 42 and 43 is positive (+) polarity, the smoothing capacitor 4 is charged by the rectifying diode 42, and when the voltage applied to the rectifying diodes 42 and 43 is negative (-) polarity, the coupling capacitor 41 is discharged by the rectifying diode 43. This operation is performed at a very fast cycle of 20Khz to 30Khz, so that a very high-quality power supply voltage VCC is formed in the smoothing capacitor 4.

[0019] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is intended to include these modifications and variations.

Claims

1. A power supply voltage generating circuit for a microwave oven inverter, characterized in that: The power supply voltage generating circuit includes a power supply voltage generating unit for supplying power supply voltage to an inverter control unit, a power semiconductor for inverter action, a high-voltage transformer for generating high voltage through inverter action, and a magnetron for emitting microwave waves through the high-voltage transformer, wherein the power supply voltage generating unit is composed of a first power supply voltage generating unit and a second power supply voltage generating unit.

2. The power supply voltage generating circuit of a microwave oven inverter according to claim 1, characterized in that: The first power supply voltage generating unit includes a current limiting resistor, a transistor, a base resistor and a base capacitor, one end of the current limiting resistor is electrically connected to the collector of the transistor, the base resistor is electrically connected to the base of the transistor through the base capacitor, and the emitter of the transistor is electrically connected to the inverter control unit.

3. The power supply voltage generating circuit of a microwave oven inverter according to claim 2, characterized in that: The first power supply voltage generating unit further includes a constant voltage diode connected between the emitter and the base resistor of the transistor.

4. A power supply voltage generating circuit for a microwave oven inverter according to claim 2 or 3, characterized in that: The second power supply voltage generating unit includes a capacitor, a first rectifier diode and a second rectifier diode. One end of the capacitor is electrically connected to the primary coil of the high-voltage transformer, and the other end of the capacitor is electrically connected to the positive electrode of the first rectifier diode and the negative electrode of the second rectifier diode, respectively.

5. The power supply voltage generating circuit of a microwave oven inverter according to claim 4, characterized in that: The cathode of the first rectifier diode is electrically connected to a constant voltage diode and a smoothing capacitor.

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