阅读说明：本技术 可切换前沿控制和后沿控制的可控硅功率放大器及其工作方法 (Silicon controlled power amplifier capable of switching leading edge control and trailing edge control and working method thereof ) 是由 不公告发明人 于 2020-12-31 设计创作，主要内容包括：本发明提供一种可切换前沿控制和后沿控制的可控硅功率放大器及其工作方法,该功率放大器包括调光信号检测电路、控制器、斩波电路、过零检测电路及选择开关电路；控制器接收调光信号检测电路输出的调光检测信号及选择开关电路输出的选择信号,控制器还接收过零检测电路输出的过零检测信号,并根据调光检测信号、过零检测信号以及选择信号向斩波电路输出脉冲调制信号。该工作方法包括调光信号检测电路接收调光器输出的调光控制信号,并对调光控制信号整流后向控制器输出调光检测信号；控制器获取过零检测信号以及选择信号,并根据调光检测信号计算向斩波电路输出的脉冲调制信号。本发明的可控硅功率放大器可以兼容前沿控制或者后沿控制两种方式。(The invention provides a silicon controlled power amplifier capable of switching leading edge control and trailing edge control and a working method thereof, wherein the power amplifier comprises a dimming signal detection circuit, a controller, a chopper circuit, a zero-crossing detection circuit and a selection switch circuit; the controller receives the dimming detection signal output by the dimming signal detection circuit and the selection signal output by the selection switch circuit, and also receives the zero-crossing detection signal output by the zero-crossing detection circuit, and outputs a pulse modulation signal to the chopper circuit according to the dimming detection signal, the zero-crossing detection signal and the selection signal. The working method comprises the steps that a dimming signal detection circuit receives a dimming control signal output by a dimmer, rectifies the dimming control signal and outputs a dimming detection signal to a controller; the controller acquires the zero-crossing detection signal and the selection signal, and calculates a pulse modulation signal output to the chopper circuit according to the dimming detection signal. The thyristor power amplifier can be compatible with a leading edge control mode or a trailing edge control mode.)

1. A thyristor power amplifier switchable between leading edge control and trailing edge control, comprising:

the dimming circuit comprises a dimming signal detection circuit, a controller, a chopper circuit, a zero-crossing detection circuit and a selective switch circuit;

the controller receives a dimming detection signal output by the dimming signal detection circuit and a selection signal output by the selection switch circuit, and also receives a zero-crossing detection signal output by the zero-crossing detection circuit, and outputs a pulse modulation signal to the chopper circuit according to the dimming detection signal, the zero-crossing detection signal and the selection signal.

2. The switchable leading-edge-controlled and trailing-edge-controlled silicon controlled power amplifier of claim 1, wherein:

the dimming signal detection circuit comprises a rectifying circuit and a first photoelectric coupler, and the first photoelectric coupler receives a signal output by the rectifying circuit and outputs the dimming detection signal to the controller.

3. A switchable leading-edge controlled and trailing-edge controlled thyristor power amplifier as claimed in claim 1 or 2, characterized in that:

the selection switch circuit has a second photocoupler that receives a key signal and outputs the selection signal to the controller.

4. A switchable leading-edge controlled and trailing-edge controlled thyristor power amplifier as claimed in claim 1 or 2, characterized in that:

the chopper circuit is provided with a first switching device and a second switching device, the first switching device and the second switching device both receive the pulse modulation signal, and the conduction levels of the first switching device and the second switching device are opposite.

5. The switchable leading-edge-controlled and trailing-edge-controlled silicon controlled power amplifier of claim 4, wherein:

the chopper circuit further comprises a third switching device and a fourth switching device, and a control end of the third switching device and a control end of the fourth switching device are both connected to a joint of the first switching device and the second switching device.

6. The switchable leading-edge-controlled and trailing-edge-controlled silicon controlled power amplifier of claim 5, wherein:

the silicon controlled power amplifier also comprises an over-power protection circuit, wherein the over-power protection circuit receives voltage signals output by the third switching device and the fourth switching device and outputs signals to the controller.

7. The method of operating a switchable leading-edge controlled and trailing-edge controlled thyristor power amplifier as claimed in any one of claims 1 to 5, wherein:

the dimming signal detection circuit receives a dimming control signal output by a dimmer, rectifies the dimming control signal and outputs a dimming detection signal to the controller;

the controller acquires a zero-crossing detection signal and a selection signal, calculates a pulse modulation signal output to the chopper circuit according to the dimming detection signal, and outputs the pulse modulation signal to the chopper circuit.

8. The operating method of a switchable leading-edge-controlled and trailing-edge-controlled thyristor power amplifier as claimed in claim 7, wherein:

and the controller determines the leading edge control or the trailing edge control according to the selection signal and calculates and outputs the pulse modulation signal to the chopper circuit according to a control mode.

9. The operating method of a switchable leading-edge-controlled and trailing-edge-controlled thyristor power amplifier as claimed in claim 7 or 8, characterized in that:

the controller calculates the duty ratio of the pulse modulation signal according to the voltage of the dimming detection signal.

10. The operating method of a switchable leading-edge-controlled and trailing-edge-controlled thyristor power amplifier as claimed in claim 7 or 8, characterized in that:

the silicon controlled power amplifier also comprises an over-power protection circuit, wherein the over-power protection circuit receives a voltage signal of the chopper circuit and outputs a signal to the controller;

and the controller judges whether the power is greater than a preset threshold value according to the signal output by the power protection circuit, and if so, the controller stops outputting the pulse modulation signal.

Technical Field

The invention relates to the field of control of intelligent lamps, in particular to a silicon controlled power amplifier capable of switching front edge control and back edge control and a working method of the silicon controlled power amplifier.

Background

Along with the development of intelligent home technology, the current household appliances are more and more intelligent, and the intelligent lamp is a common intelligent appliance. The existing intelligent lamp is generally provided with an LED chip, and the brightness of the LED chip can be adjusted through a dimmer, so that the dimming of the intelligent lamp is realized.

With the continuous development of dimming technology, various dimming technologies emerge in a wide range, wherein the silicon controlled dimming technology is a common dimming technology, has the advantage of simple installation method, and is completely compatible with the traditional LED light source driving on the input/output circuit interface. If the traditional LED light source driving mode needs to be replaced by the silicon controlled rectifier dimming mode, the traditional LED light source driving mode only needs to be replaced by the LED light source driving mode capable of supporting the silicon controlled rectifier dimming, and the original wall switch is replaced by the silicon controlled rectifier dimmer to conduct dimming, so that the silicon controlled rectifier dimming technology is widely applied to the process of modifying the intelligent lamp.

The current silicon controlled rectifier dimming control mode has a silicon controlled rectifier dimmer with low power, such as a knob type silicon controlled rectifier dimmer, and also has a system type silicon controlled rectifier dimming device with high power. In addition, the silicon controlled rectifier dimming technology has two dimming modes, namely a leading edge control mode and a trailing edge control mode. Referring to fig. 1, for a half-wave period of a sine wave, if a leading edge control method is adopted, after an alternating current zero-crossing point, chopping is performed backward from the zero-crossing point, for example, a hatched portion in fig. 1 is a chopped portion, for example, the chopping proportion is 30%, the output dimming proportion is 70%, that is, the light-emitting brightness of the LED chip is 70% of the maximum light-emitting brightness, and the arrow in the figure is the direction of chopping. Referring to fig. 2, if the trailing edge control mode is adopted, the chopping is performed forward from the zero crossing point, for example, the hatched portion in fig. 2 is the chopped portion, and the arrow in the figure is the direction of the chopping.

Generally, the compatibility requirement of the front-edge control dimmer on the driving of the rear-stage LED light source is high, while the compatibility requirement of the rear-edge control dimmer on the driving of the rear-stage LED light source is relatively low, but for the control of the driving of the LED light source, the experience feeling of the rear-edge control dimming mode is better, so the front-edge control mode and the rear-edge control mode have respective advantages and disadvantages.

Generally speaking, if the knob type light modulator adopts a leading edge control light modulation mode, the output power is high, and the driving power of the driven LED light source can reach 300W to 500W; if a trailing edge control mode is adopted, the power of the LED light source driving is usually 200W to 300W, so that the driving quantity of the thyristor LED light sources which can be controlled by the rear stage is not large.

The system type dimmer generally has multiple outputs, and the trailing edge control mode is common, assuming that the power of each output is 300W, and the system has four outputs, the total power can also reach 1200W, which cannot be realized for the knob type dimmer, resulting in the limited use of the knob type dimmer. Of course, the system-like dimmer is also expensive.

In addition, different LED light source driving methods may choose to use the leading edge control method for dimming due to the limitations of their own structures, because such a dimmer using the trailing edge control method has poor dimming effect. However, if the current dimmer is exactly a trailing-edge controlled dimmer, the current dimmer cannot meet the use requirement, so that the current dimmer cannot meet the use requirement of various occasions.

Disclosure of Invention

The first purpose of the invention is to provide a thyristor power amplifier which can switch leading edge control and trailing edge control and can meet the requirements of various occasions.

The second purpose of the present invention is to provide an operating method of the thyristor power amplifier capable of switching between leading edge control and trailing edge control.

In order to achieve the first purpose of the invention, the silicon controlled power amplifier capable of switching leading edge control and trailing edge control comprises a dimming signal detection circuit, a controller, a chopper circuit, a zero-crossing detection circuit and a selection switch circuit; the controller receives the dimming detection signal output by the dimming detection signal detection circuit and the selection signal output by the selection switch circuit, and also receives the zero-crossing detection signal output by the zero-crossing detection circuit and outputs a pulse modulation signal to the chopper circuit according to the dimming signal, the zero-crossing detection signal and the selection signal.

According to the scheme, a user can select a leading edge control mode or a trailing edge control mode to perform dimming according to needs, for example, a selection switch circuit sends a selection signal to a controller, namely, the leading edge control or the trailing edge control is selected, the microcontroller controls the chopping direction of the pulse modulation signal according to the selection signal, so that the switching between the leading edge control mode and the trailing edge control mode is realized, and the user can independently select the leading edge control mode or the trailing edge control mode.

In a preferred embodiment, the dimming signal detection circuit includes a rectifying circuit and a first photocoupler, and the first photocoupler receives a signal output by the rectifying circuit and outputs the dimming detection signal to the controller.

Therefore, the signal output by the dimmer is isolated through the first photoelectric coupler, so that the impact of large current on a rear-stage controller can be avoided, and the stable operation of the controller is ensured.

The further scheme is that the selection switch circuit is provided with a second photoelectric coupler, and the second photoelectric coupler receives the key signal and outputs a selection signal to the controller.

Therefore, when the user changes the dimming control mode, only the state of the key needs to be changed, namely the high and low levels of the key signal are changed, and the operation is very simple.

In a further aspect, the chopper circuit has a first switching device and a second switching device, the first switching device and the second switching device both receive the pulse modulated signal, and the conduction levels of the first switching device and the second switching device are opposite.

It follows that chopping of the alternating current can be achieved by the opposite conduction level states of the first switching device and the second switching device.

In a further aspect, the chopper circuit further includes a third switching device and a fourth switching device, and a control terminal of the third switching device and a control terminal of the fourth switching device are both connected to a junction of the first switching device and the second switching device.

In a further aspect, the scr power amplifier further includes an over-power protection circuit, which receives the voltage signals output by the third switching device and the fourth switching device and outputs the signals to the controller.

It can be seen that the overpower protection circuit can receive the voltage of the chopper circuit, so that the voltage of the chopper circuit is monitored, and once the voltage of the chopper circuit is overlarge, the controller can stop outputting the pulse modulation signal, so that the chopper circuit is prevented from working in an overpower state for a long time, and the LED chip is prevented from being damaged.

In order to achieve the second objective, the present invention provides a working method of the above-mentioned thyristor power amplifier capable of switching between leading edge control and trailing edge control, including that the dimming signal detection circuit receives the dimming control signal output by the dimmer, rectifies the dimming control signal, and outputs the dimming detection signal to the controller; the controller acquires the zero-crossing detection signal and the selection signal, calculates a pulse modulation signal output to the chopper circuit according to the dimming detection signal, and outputs the pulse modulation signal to the chopper circuit.

According to the scheme, a user can select a leading edge control mode or a trailing edge control mode to perform dimming according to needs, namely, a selection signal is sent to the controller through the selection switch circuit, the microcontroller changes the chopping direction of the pulse modulation signal according to the selection signal, so that the adjustment of the leading edge control mode and the trailing edge control mode is realized, and the user can independently select the leading edge control mode or the trailing edge control mode.

Preferably, the controller determines the leading edge control or the trailing edge control according to the selection signal, and calculates to output the pulse modulation signal to the chopper circuit according to the control mode.

Therefore, the pulse modulation signal output by the controller is the pulse modulation signal calculated according to the leading edge control mode or the trailing edge control mode selected by the user, and flexible adjustment of leading edge control and trailing edge control can be ensured.

Further, the controller calculates a duty ratio of the pulse modulation signal according to a voltage of the dimming detection signal.

Therefore, the signal output by the silicon controlled rectifier dimmer is a voltage signal which changes according to different conduction angles, the dimming detection signal output by the dimming signal detection circuit reflects the change of the conduction angle, and the controller calculates the duty ratio of the corresponding pulse modulation signal according to the dimming detection signal, so that the consistency of the luminous brightness of the LED chip and the dimming control signal of the dimmer can be ensured.

The silicon controlled power amplifier further comprises an over-power protection circuit, wherein the over-power protection circuit receives a voltage signal of the chopper circuit and outputs a signal to the controller; the controller judges whether the power is larger than a preset threshold value according to the signal output by the power protection circuit, and if so, the controller stops outputting the pulse modulation signal.

Therefore, the over-power protection circuit can receive the voltage of the chopper circuit, so that the voltage of the chopper circuit is monitored, and once the voltage of the chopper circuit is too large, the controller can stop outputting the pulse modulation signal, so that the chopper circuit is prevented from working in an over-power state for a long time, and the LED chip is prevented from being damaged.

Drawings

Fig. 1 is a waveform diagram of the leading edge control mode.

Fig. 2 is a waveform diagram of the trailing edge control scheme.

Fig. 3 is a block diagram of an embodiment of a thyristor power amplifier switchable between leading edge control and trailing edge control in accordance with the present invention.

Fig. 4 is an electrical schematic diagram of a dimming signal detection circuit in an embodiment of a thyristor power amplifier of the present invention switchable between leading edge control and trailing edge control.

Fig. 5 is an electrical schematic diagram of a zero crossing detection circuit in an embodiment of a thyristor power amplifier of the present invention switchable between leading edge control and trailing edge control.

Fig. 6 is an electrical schematic diagram of a selection switch circuit in an embodiment of a thyristor power amplifier of the present invention that can switch leading edge control and trailing edge control.

Fig. 7 is an electrical schematic diagram of a controller in an embodiment of the thyristor power amplifier of the present invention that can switch leading edge control and trailing edge control.

Fig. 8 is an electrical schematic diagram of a chopper circuit in an embodiment of a thyristor power amplifier of the present invention switchable between leading edge control and trailing edge control.

Fig. 9 is an electrical schematic diagram of an over-power protection circuit in an embodiment of a thyristor power amplifier of the present invention switchable between leading edge control and trailing edge control.

Fig. 10 is a flow chart of an embodiment of the operating method of the thyristor power amplifier switchable between leading edge control and trailing edge control according to the invention.

Fig. 11 is a waveform diagram of an ac signal and a pulse modulated signal in the leading edge control mode.

Fig. 12 is a waveform diagram of an ac signal and a pulse modulated signal in the trailing edge control mode.

The invention is further explained with reference to the drawings and the embodiments.

Detailed Description

The controllable silicon power amplifier capable of switching the front edge control and the back edge control is applied to an intelligent lamp, and can compatibly realize a front edge control mode and a back edge control mode, so that the flexibility of dimming of the intelligent lamp is improved.

The controllable silicon power amplifier embodiment that can switch over leading edge control and trailing edge control:

referring to fig. 3, the present embodiment includes a dimming signal detection circuit 11, a zero-cross detection circuit 12, a selection switch circuit 13, a controller 14, a chopper circuit 15, and an overpower protection circuit 16. The dimming signal detection circuit 11 receives a dimming control signal outputted from the dimmer, and typically, the dimmer receives an ac signal, for example, 220V or 50Hz mains power, and the dimmer adjusts the conduction angle of the ac power of 180 ° in a half cycle, so that the conduction angle of the dimming control signal varies in a range of 0 to pi (i.e., 0 to 180 °).

After acquiring the dimming control signal, the dimming signal detection circuit 11 rectifies the dimming control signal and outputs the rectified dimming control signal to the controller 14. In addition, the controller 14 also receives a zero-crossing detection signal output by the zero-crossing detection circuit 12, the zero-crossing detection circuit 12 detects the time of the zero-crossing point of the alternating current signal and sends the zero-crossing detection signal to the controller 14 when the alternating current crosses the zero-crossing point, and the controller 14 determines the switching time of each period of the pulse modulation signal according to the zero-crossing detection signal, namely determines the starting time of each period.

The selection switch circuit 13 has a key, and a user can change the state of the selection switch circuit 13 and change the level signal output by the selection switch circuit 13 through the key, thereby realizing the change of the leading edge control and the trailing edge control.

The controller 14 generates a pulse modulation signal according to the dimming detection signal output by the dimming signal detection circuit 11, the zero-cross detection signal output by the zero-cross detection circuit 12, and the selection signal output by the selection switch circuit 13, and outputs the pulse modulation signal to the chopper circuit 15, and the chopper circuit 15 chops the alternating current according to the pulse modulation signal and supplies power to the LED chip serving as a load, thereby adjusting the light emission brightness of the LED chip.

In order to avoid the situation that the LED chip is burned out due to the overhigh power of the LED film, the embodiment further provides the overpower protection circuit 16, the overpower protection circuit 16 collects the voltage loaded on the LED chip by the chopper circuit 15, and judges whether the voltage loaded on the LED chip is overhigh, when the voltage loaded on the LED chip is overhigh, a signal is output to the controller 14, and the controller 14 immediately stops outputting the pulse modulation signal, so that the LED chip is prevented from operating in an overpower state for a long time.

Referring to fig. 4, the dimming signal detection circuit 11 includes a connection terminal J1 for receiving a dimming control signal output by a dimmer, the dimming control signal is an ac signal having a conduction angle in a range of 0 to pi, the dimming control signal is output to the rectifier circuits DB1 and DB2 after passing through the discharge tube Z2, the voltage dependent resistors TVR2 and TVR4, and the rectifier circuits DB1 and DB2 rectify the ac signal. The rear stage of the rectifying circuit DB1 is connected to a load circuit, so that the current output from the rectifying circuit DB1 forms a current in the load circuit, thereby preventing the dimmer from stopping working due to an excessively small overall load of the dimming signal detection circuit 11. Preferably, a plurality of voltage stabilizing diodes are arranged in the load circuit to ensure the voltage of the load circuit to be stable.

The rear stage of the rectifying circuit DB2 is connected to a photocoupler U4, the output terminal of the rectifying circuit DB2 is connected to the light emitting diode of the photocoupler U4, and the output terminal of the phototriode of the photocoupler U4 is connected to a dimming detection signal ADC1 output to the controller 14. When the conduction angle of the dimming control signal output by the dimmer is large, the voltage of the dimming control signal is also large, the brightness of the light emitting diode of the photoelectric coupler U4 is large, and the voltage of the dimming detection signal ADC1 output by the photoelectric triode is high. Conversely, when the conduction angle of the dimming control signal output by the dimmer is small, the voltage of the dimming control signal is also low, the luminance of the light emitting diode of the photocoupler U4 is small, and the voltage of the dimming detection signal ADC1 output by the phototriode is low.

In addition, since the rated voltage of the controller 14 is 5V, the voltage of the dimming detection signal ADC1 cannot be too high, and in this embodiment, the voltage of the dc power VCC connected to the output terminal of the phototransistor of the photocoupler U4 is 5V, and therefore, the voltage of the dimming detection signal ADC1 is between 0 and 5V.

Referring to fig. 5, the zero-cross detection circuit 12 includes a photocoupler U7 and a transistor Q10, and two terminals of a light emitting diode of the photocoupler U4 receive voltages of the live line L1 and the neutral line N, respectively. The base of the transistor Q10 is connected to the output of the photo-transistor of the photocoupler U7, and the collector of the transistor Q10 outputs a zero-crossing detection signal to the controller 14.

In the positive half cycle of the alternating current, the voltage of the live wire connecting terminal L1 is higher than the voltage of the zero line connecting terminal N, the light emitting diode of the photoelectric coupler U7 emits light, the photoelectric triode is conducted, at the moment, the base electrode of the triode Q10 is at a high level, and the collector electrode of the triode Q10 outputs a high level signal, namely, the zero-crossing detection signal is a high level signal. In the negative half cycle of the alternating current, the voltage of the live wire connecting terminal L1 is lower than the voltage of the zero line connecting terminal N, the light emitting diode of the photoelectric coupler U7 does not emit light, the photoelectric triode is not conducted, at the moment, the base electrode of the triode Q10 is at a low level, and the collector electrode of the triode Q10 outputs a low level signal, namely, the zero-crossing detection signal is a low level signal. When the positive half cycle and the negative half cycle of the alternating current are switched, namely the alternating current crosses zero, the level of the zero-crossing detection signal is changed, namely, the level is switched from high level to low level, or the level is switched from low level to high level. The controller 14 determines the time when the alternating current crosses zero according to the change of the high and low levels of the zero-crossing detection signal.

Referring to fig. 6, the selection switch circuit 13 has a KEY K1 and a photo coupler U10, a KEY signal output from the KEY K1 is received by the photo coupler U10, and an output terminal of the photo coupler U10 outputs a selection signal KEY to the controller 14. For example, the KEY K1 has two states of on and off, in which the levels of the KEY signals are opposite, for example, when the KEY K1 is pressed, the KEY signal is at high level, the light emitting diode of the photocoupler U10 emits light, the phototriode is turned on, and the selection signal KEY is at high level. When the KEY K1 is turned on, the KEY signal is at a low level, the light emitting diode of the photoelectric coupler U10 does not emit light, the phototriode is not turned on, and the selection signal KEY is a low level signal. Thus, the two states of key K1 may represent the manner of leading edge control or trailing edge control, respectively.

Preferably, the output terminal of the phototriode is connected to a dc power source VCC, and the dc power source VCC is a 5V dc power source, so that the problem of too high voltage of the selection signal output to the controller 14 can be avoided.

Referring to fig. 7, the controller 14 includes a single chip U1, and the single chip U1 has one pin receiving the dimming detection signal ADC1, another pin receiving the selection signal KEY, and another pin receiving the zero-crossing detection signal. The single chip microcomputer U1 determines the starting time of each period of the pulse modulation signal according to the zero-crossing detection signal, calculates the duty ratio of the pulse modulation signal according to the dimming detection signal ADC1, judges whether the control mode currently set by the user is the leading edge control mode or the trailing edge control mode according to the selection signal, and determines the chopping starting time of the pulse modulation signal. The method by which the controller 14 calculates the pulse modulated signal will be described in detail later.

The controller 14 may output four pulse modulation signals, i.e., PWM1, PWM2, PWM3, and PWM4, to the four chopper circuits, respectively, to control four different LED chips. In practical application, one single chip microcomputer can output more multi-path pulse modulation signals, so that more LED chips are controlled.

Referring to fig. 8, the chopper circuit 15 receives a pulse modulation signal, such as a PWM1 signal, and receives an ac electrical signal, and chops the ac electrical signal according to the pulse modulation signal. The chopper circuit has a transistor Q14 as a first switching device and a transistor Q16 as a second switching device, and further, a field effect transistor Q1 as a third switching device and a field effect transistor Q2 as a fourth switching device are provided. The transistor Q14 is a high-level conducting switch device, the transistor Q16 is a low-level conducting switch device, and the field-effect transistors Q1 and Q2 are high-level conducting switch devices. Further, the chopper circuit is electrically connected to the LED chip through the connection terminal J3 and outputs a chopper signal.

When the pulse modulation signal is a high level signal, the transistor Q14 is turned on, the transistor Q16 is turned off, at this time, the current output by the +15V dc power supply flows through the transistor Q14, the resistors R37 and R40 form a high level signal, and since the gates (i.e., control ends) of the fets Q1 and Q2 are both connected to the connection of the transistors Q14 and Q16, the fets Q1 and Q2 are both turned on. At this time, the positive half cycle of the alternating current may pass through the live line L and flow through the LED chip, pass through the LED chip as a load, and then pass through the field effect transistor Q1; the negative half cycle of the alternating current may pass through the neutral line N and through the LED chip, through the LED chip as a load, and then through the fet Q2. Therefore, when the pulse modulation signal is at a high level, a current flows through the LED chip.

When the pulse modulation signal is a low level signal, the triode Q14 is turned off, the triode Q16 is turned on, at this time, the current output by the +15V dc power supply cannot flow through the triode Q14, the resistors R37 and R40 form a low level signal, and the field effect transistors Q1 and Q2 are both turned off. At this time, the alternating current cannot pass through the field effect transistors Q1 and Q2 to form a path, and no current flows through the LED chip, so that chopping of the alternating current is realized.

Referring to fig. 9, the over-power protection circuit 16 has two voltage detection terminals, one of which is connected to one end of the resistor R39 of the chopper circuit 15 to collect the voltage across the resistor R39, and the other of which is connected to one end of the resistor R40 of the chopper circuit 15 to collect the voltage across the resistor R40. Since the resistors R39 and R40 are connected to the outputs of the fets Q1 and Q2, respectively, the over-power protection circuit 16 effectively collects the voltage applied to the LED chip.

The over-power protection circuit 16 is further provided with a voltage comparator U2, the voltage comparator U2 is configured to compare the collected voltage signal, for example, with a preset threshold, if the collected voltage is higher than the preset threshold, it indicates that the voltage applied to the LED chip by the chopper circuit 15 is too high, at this time, the voltage comparator U2 sends a signal to the controller 14, and the controller 14 immediately stops outputting the pulse modulation signal, so as to prevent the LED chip from operating in an over-power state for a long time. If the voltage collected by the over-power protection circuit 16 is not higher than the preset threshold, it indicates that the voltage applied to the LED chip by the chopper circuit 15 is normal, and at this time, the voltage comparator U2 does not send a signal to the controller 14.

The working method embodiment of the controllable silicon power amplifier capable of switching leading edge control and trailing edge control comprises the following steps:

the operation of the thyristor power amplifier will now be described with reference to figure 10. First, step S1 is executed, and the dimming signal detection circuit receives the dimming control signal output by the dimmer. The dimming control signal output by the dimmer is a signal with a variable conduction angle, and the voltage of the dimming control signal changes along with the change of the conduction angle.

The dimming detection circuit rectifies the dimming control signal after receiving the dimming control signal, and outputs a corresponding dimming detection signal according to the magnitude of the dimming control signal, that is, the magnitude of the dimming detection signal is positively correlated with the magnitude of the dimming control signal, for example, the magnitude of the voltage of the dimming detection signal and the magnitude of the voltage of the dimming control signal are linearly changed.

Then, step S2 is executed, and the dimming control circuit outputs the dimming detection signal to the controller. Next, the controller performs step S3 to receive the zero-cross detection signal and the selection signal, and performs step S4 to generate a corresponding pulse modulation signal according to the dimming detection signal, the zero-cross detection signal, and the selection signal. Specifically, the controller calculates a period of each pulse modulation signal according to the zero-crossing detection signal, that is, a period of one pulse modulation signal is a time between two adjacent zero-crossing points, that is, each zero-crossing point is a start point of one period of the pulse modulation signal. The dimming detection signal is used for calculating the duty ratio of the pulse modulation signal, and specifically, the controller calculates the duty ratio of the pulse modulation signal according to the voltage magnitude of the dimming detection signal, and the larger the voltage of the dimming detection signal is, the larger the duty ratio of the pulse modulation signal is, the smaller the voltage of the dimming detection signal is, and the smaller the duty ratio of the pulse modulation signal is.

The selection signal is used to determine the start of the chopping of the pulse modulated signal, i.e. whether the chopping is started from the leading edge instant or from the trailing edge instant of a cycle. Referring to fig. 11, if the selection signal is characterized by leading edge control for chopping, a low level signal is output at the beginning of one period of the pulse modulation signal, i.e., chopping is started from the leading edge. Referring to fig. 12, if the selection signal is characterized by the trailing-edge control mode for chopping, a high signal is output at the beginning of one period of the pulse modulation signal, and a low signal is output at the latter part of the period, that is, chopping is started from the trailing-edge time. Since the period of the pulse modulation signal is generally fixed, after the start time of one period of the pulse modulation signal is determined and the duty ratio of the period is determined, the duration of the high-level signal and the duration of the low-level signal of the pulse modulation signal in the period can be calculated, so as to determine the waveform of the pulse modulation signal.

After the controller outputs the pulse modulation signal to the chopper circuit, the chopper circuit loads voltage to the LED chip, the LED chip emits light, the over-power protection circuit receives the voltage of the chopper circuit, step S5 is executed, whether the voltage of the chopper circuit is too high is judged, for example, whether the voltage is higher than a preset threshold value is judged, if yes, step S6 is executed, a signal is sent to the controller, the controller stops outputting the pulse modulation signal immediately, and the LED chip is prevented from being damaged due to long-time operation in an over-power state. If the voltage of the chopper circuit is not too high, the controller continues to output the pulse modulated signal to the chopper circuit.

Therefore, by arranging the selection switch circuit, a user can determine to use a front edge control mode or a back edge control mode according to actual needs, the same silicon controlled power amplifier can be compatible with two different control modes, the use requirements under different scenes are met, and the compatibility of the silicon controlled power amplifier is better.

Finally, it should be emphasized that the present invention is not limited to the above-mentioned embodiments, for example, the specific circuit structure of the dimming signal detection circuit is changed, or the number of pulse modulation signals outputted by the controller is changed, and such changes should also be included in the protection scope of the claims of the present invention.