A load control circuit

Abstract

The utility model provides a kind of load control circuit, including discharge circuit, optocoupler module U8 and heating circuit, the heating circuit includes fire line ACL, zero line ACN, thyristor T1 and heating wire H1, the anode A of thyristor T1 is connected heating wire H1, cathode C connects the zero line ACN, another end of the heating wire H1 is connected fire line ACL, the discharge circuit includes capacitor C33 and resistance one R15, one end of capacitor C33 is connected with control chip IC1, another end is connected with resistance one R15, another end of resistance one R15 is connected with the pin 1 of optocoupler module, the pin 2 of optocoupler module U8 is grounded, and pin 3 is connected the control electrode K of thyristor T1;After control chip IC1 detects zero crossing point F signal, it sends jump edge signal, capacitor C33 discharges, and in the discharge process, control chip IC1 output pulse signal simultaneously has zero crossing point F signal generation to make optocoupler module U8 conduction, and then conduction thyristor T1 makes the heating circuit form loop heating work.

Description

Technical Field

[0001] This utility model belongs to the field of power supply circuit technology, specifically relating to a load control circuit. Background Technology

[0002] Traditional load control circuits typically use a microcontroller to directly control the input of an optocoupler to drive a thyristor, thereby controlling the heat-generating load. However, this design has a serious flaw: if the microcontroller malfunctions or the software fails and continuously outputs a high or low level, the optocoupler will remain on, causing the thyristor to be continuously triggered. This results in the load being powered on for an extended period, which may lead to overheating or even burnout, posing a safety hazard. Utility Model Content

[0003] (1) Technical problems to be solved

[0004] This invention provides a load control circuit, which aims to solve the problem that the continuous output of a fixed level by a microcontroller causes the load to be continuously powered and thus damaged.

[0005] (2) Technical solution

[0006] This utility model provides a load control circuit, including a discharge circuit, an optocoupler module U8, and a heating circuit. The heating circuit includes a live wire ACL, a neutral wire ACN, a silicon controlled rectifier (SCR) T1, and a heating wire H1. The anode A of the SCR T1 is connected to the heating wire H1, and the cathode C is connected to the neutral wire ACN. The other end of the heating wire H1 is connected to the live wire ACL. The discharge circuit includes a capacitor C33 and a resistor R15. One end of the capacitor C33 is connected to the control chip IC1, and the other end is connected to the resistor R15. The other end of the resistor R15 is connected to pin 1 of the optocoupler module. Pin 2 of the optocoupler module U8 is grounded, and pin 3 is connected to the control electrode K of the SCR T1.

[0007] When the control chip IC1 detects the zero-crossing F signal, it sends a transition edge signal. The capacitor C33 discharges. During the discharge process, the control chip IC1 outputs a pulse signal and simultaneously generates the zero-crossing F signal, which turns on the optocoupler module U8. This, in turn, turns on the thyristor T1, causing the heating circuit to form a loop and start heating.

[0008] Furthermore, the discharge time of the capacitor C33 is a constant τ, where the discharge time constant τ = resistance - R15 × capacitor C33.

[0009] Furthermore, the discharge time constant τ satisfies: τ < half a mains power cycle.

[0010] Furthermore, the conduction time t3 of the thyristor T1 is at least partially after the zero-crossing point F, and t3 < τ.

[0011] Furthermore, after the control chip IC1 detects the zero-crossing point F, it outputs the transition edge signal after a delay time t1, wherein the delay time t1 satisfies: t1≤half of the mains power cycle.

[0012] Furthermore, the delay time t1 plus the discharge time τ must be greater than half a mains power cycle, that is, t1+τ> half a mains power cycle.

[0013] Furthermore, the pulse signal output by the control chip IC1 is basically synchronized with the zero-crossing point F signal.

[0014] Furthermore, the thyristor T1 is a bidirectional thyristor.

[0015] Furthermore, it also includes resistor R19, one end of which is connected to pin 4 of the optocoupler module U8, and the other end is connected between the heating wire H1 and the anode A of the thyristor T1.

[0016] Furthermore, it also includes a resistor R32, which together with the capacitor C33 forms a charging circuit. One end of the resistor R32 is grounded to GND, and the other end is connected to the capacitor C33.

[0017] Compared with the prior art, the beneficial effects of this utility model are as follows: By connecting capacitor C33 in series at the input end of optocoupler module U8, the characteristic of capacitors to pass AC and block DC is utilized to block the fixed level output of control chip IC1, ensuring that optocoupler module U8 only responds to the transition edge signal. Even if control chip IC1 loses control and continuously outputs high or low level, optocoupler module U8 will not conduct, completely eliminating the risk of continuous power supply to the load. Attached Figure Description

[0018] Figure 1 This is a circuit diagram of the present invention.

[0019] Figure 2 This is a waveform diagram of the present invention.

[0020] Figure 3 This is a comparison diagram of the thyristor and pulse signal waveforms of this utility model.

[0021] Figure 4 This is a schematic diagram of the discharge circuit of this utility model.

[0022] Figure 5 This is a schematic diagram of the charging circuit of this utility model.

[0023] Figure 6 This is a schematic diagram of the zero-crossing detection circuit of this utility model.

[0024] Figure 7 This is a schematic diagram of the control chip of this utility model.

[0025] Figure labels: 1-Discharge circuit, 2-Heating circuit, 3-Charging circuit, 4-Zero-crossing detection circuit. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention.

[0027] like Figure 1 As shown, this utility model provides a load control circuit, including a discharge circuit 1, an optocoupler module U8, and a heating circuit 2. The heating circuit 2 includes a live wire ACL, a neutral wire ACN, a silicon controlled rectifier (SCR) T1, and a heating wire H1. The anode A of the SCR T1 is connected to the heating wire H1, and the cathode C is connected to the neutral wire ACN. The other end of the heating wire H1 is connected to the live wire ACL. The discharge circuit 1 includes a capacitor C33 and a resistor R15. One end of the capacitor C33 is connected to the control chip IC1, and the other end is connected to the resistor R15. The other end of the resistor R15 is connected to pin 1 of the optocoupler module. Pin 2 of the optocoupler module U8 is grounded, and pin 3 is connected to the control electrode K of the SCR T1.

[0028] In use, after the control chip IC1 detects the zero-crossing F signal, it sends a rising edge signal, and the capacitor C33 discharges. During the discharge process, the control chip IC1 outputs a pulse signal and simultaneously generates the zero-crossing F signal, which turns on the optocoupler module U8, thereby turning on the thyristor T1 and causing the heating circuit 2 to form a loop and start heating.

[0029] In traditional designs, the optocoupler input is directly controlled by a microcontroller. If the microcontroller malfunctions or has a program error, it will continuously output a high or low level, causing the optocoupler module to remain continuously conducting. This results in the thyristor being constantly triggered, leading to prolonged power supply to the load and potentially causing overheating and burnout. This application addresses this issue by connecting a capacitor C33 in series between the optocoupler modules U8 and the optocoupler input, instead of directly connecting the optocoupler module U8 to the control chip IC1. The capacitor has the characteristic of passing AC and blocking DC. By connecting the capacitor C33 in series, the fixed output level of the control chip IC1 is blocked by the capacitor. Even if the control chip IC1 malfunctions and continuously outputs a high or low level, the capacitor's DC blocking effect prevents the optocoupler module U8 from continuously receiving a signal. This prevents the signal from being directly transmitted to the optocoupler module U8, thus preventing the thyristor T1 from conducting and causing the heating wire H1 to overheat and burn out.

[0030] In this embodiment, the discharge time of the capacitor C33 is set to a constant τ, where the discharge time constant τ = resistance - R15 × capacitor C33.

[0031] Furthermore, the discharge time constant τ satisfies: τ < half a mains power cycle.

[0032] At the discharge time τ, a zero-crossing F signal is generated.

[0033] like Figure 2 and Figure 3 As shown, in an AC voltage or voltage waveform, the point where the instantaneous value is 0 is called the zero point. In this embodiment, the input is 220V / 50Hz, and the AC current is a sine wave. There are two zero crossings in one cycle, including crossing the zero point from the positive half-cycle to the negative half-cycle, or crossing the zero point from the negative half-cycle to the positive half-cycle. The instant the AC signal crosses the zero point is the zero-crossing point F. In this embodiment, the input mains power is 50Hz, that is, 20ms is one cycle, and the zero-crossing point F occurs once every 10ms. The transition from the positive half-wave to the negative zero-crossing point F is the falling edge, and the transition from the negative half-wave to the positive zero-crossing point F is the rising edge. Since the thyristor T1 is the device that controls the switching of the load heating wire H1, it can only be guaranteed that the thyristor is stably turned on in the entire half-cycle if it is triggered near the zero-crossing point F. If it is turned on outside the zero-crossing point F, the surge current will be generated due to the excessively high instantaneous voltage value, which may damage the device.

[0034] When in use, when the control chip IC1 detects the zero-crossing point F of the mains power, it outputs a synchronous pulse signal SCR DIV_1. During this pulse window, the transition edge (rising edge or falling edge) output by the control chip IC1 can trigger the optocoupler module U8 through the capacitor 33.

[0035] like Figure 4 and Figure 5 As shown, when balanced (A=B=C=0V), the SCR DIV_1 control terminal experiences a rising edge, meaning A=5V. Since capacitor C33 cannot change voltage instantaneously, to maintain the AB voltage difference at 0V, terminal B is at 5V. Discharge to terminal C occurs through resistor R15 and the input terminal of optocoupler module U8. During the discharge process, if a zero-crossing signal arrives, pins 3 and 4 of the optocoupler module U8 will conduct. After the discharge is complete, A=5V, B=C=0V, and the AB voltage difference is 5V. When the SCR DIV_1 control terminal experiences a falling edge, meaning A=0V, since capacitor C33 cannot change voltage instantaneously, to maintain the 5V voltage difference, B=-5V. Terminal C then charges terminal B through resistor R32. In summary, utilizing the characteristic of capacitor C33 to pass AC and block DC, optocoupler module U8 can only be turned on when a rising edge signal arrives.

[0036] When in use, when the control chip IC1 detects the zero crossing point F, it outputs a transition edge signal after a delay time t1 to discharge. The delay time t1 satisfies: t1≤half of the mains power cycle.

[0037] The discharge time τ lasts for t2. During the t2 interval of the discharge time τ, when a zero-crossing point F is generated, the control chip IC1 sends a pulse signal to trigger the optocoupler module U8 to conduct. This pulse signal is synchronized with the mains zero-crossing signal. The optocoupler module U8 will output a signal to conduct the thyristor T1. After the thyristor T1 is conducted, the heating circuit 2 forms a loop and conducts, and the heating wire H1 is energized and heats up.

[0038] Specifically, the time for the thyristor T1 to be turned on (the time for triggering the thyristor T1 to turn on) within the discharge time τ after the zero-crossing point F is t3. At this time, t3 < discharge time τ < 10ms (50Hz half cycle). If the discharge time τ is too long, such as greater than 10ms, it will cause capacitor C33 to fail to reset, thus missing the next zero-crossing point F, which will cause the load to fail to be triggered.

[0039] It should be noted that if the control chip IC1 continuously outputs a high level (DC), the input voltage of the optocoupler module U8 will return to zero after the DC is blocked by capacitor C33, causing the optocoupler module U8 to be unable to conduct. However, the control chip IC1 of this application outputs a transition edge signal, generating an instantaneous current, which makes the optocoupler module U8 conduct, thereby triggering the thyristor T1, so that the load is only energized near the zero-crossing point F.

[0040] Furthermore, the delay time t1 + discharge time τ(t2) is greater than the half-wave time 10ms, and the delay time t1 and discharge time τ correspond to... Figure 3 The t2 time period must be less than 10ms (half a cycle of 50Hz mains power) to ensure that the reset is completed before the next zero crossing point F. If the control chip IC1 does not output a new transition edge during the discharge time τ, the capacitor voltage is stable and the optocoupler module U8 is automatically turned off. This design ensures that even if the control chip IC1 outputs a fixed level, the optocoupler module U8 will only respond to the transition edge due to the DC blocking effect of capacitor C33, thus completely preventing the load from being continuously powered.

[0041] In this embodiment, the transition edge signal is SCR DIV_1.

[0042] Specifically, such as Figure 4 As shown, it also includes a charging circuit 3, which includes a resistor R32. One end of the resistor R32 is connected to the capacitor C33, and the other end is grounded to GND. That is, charging is performed during the period from the completion of the discharge circuit 1 to the next zero crossing point F. In other words, when there is no edge signal, the capacitor C33 is slowly charged to a stable voltage through the resistor R32.

[0043] Furthermore, the thyristor T1 is a bidirectional thyristor, and the bidirectional thyristor T1 is a full-wave circuit, corresponding to the AC half-wave synchronization when the signal SCR DIV_1 issued by the control chip IC1 turns on the thyristor T1.

[0044] Specifically, it also includes resistor R19, one end of which is connected to pin 4 of the optocoupler module U8, and the other end is connected between the heating wire H1 and the anode A of the thyristor T1. By setting resistor R19, the trigger current is limited, thus protecting the optocoupler module U8 and the thyristor T1.

[0045] Preferably, it also includes a resistor R14, one end of which is connected to pin 3 of the optocoupler module U8, and the other end is connected to the control electrode K of the thyristor T1. By designing the resistor R14, the input terminal of the optocoupler module U8 is protected from excessive current surges.

[0046] Preferably, it includes resistor R47, one end of which is connected between resistor R14 and the control electrode K of the thyristor T1, and the other end is connected to the neutral line ACN. By designing resistor R47, when the thyristor T1 is turned on, the current will flow through resistor R47, thereby limiting the current flowing through the thyristor T1 and preventing excessive current from damaging the thyristor T1 or the heating wire H1.

[0047] When in use, when the thyristor T1 is turned on, the optocoupler module U8 provides trigger current to the control electrode K of the thyristor T1 through conduction. The current starts from the AC power supply ACL, passes through the heating wire H1 and the turned-on thyristor T1, and returns to the AC power supply ACN to form a circuit.

[0048] Specifically, such as Figure 6 As shown, it also includes a zero-crossing detection circuit 4, which generates a zero-crossing point F signal. The control chip IC1 receives the signal from the zero-crossing detection circuit 4 and then decides whether to output a transition edge signal, thereby controlling the conduction of the thyristor T1.

[0049] Control chip IC1, such as Figure 7 As shown.

[0050] The load control circuit described in this application is applicable to a variety of electronic devices, such as high-speed hair dryers, electric hair dryers, or heaters.

[0051] The following is a detailed explanation of the working principle of this utility model;

[0052] When the control chip IC1 detects the zero-crossing point F of the mains power, it outputs a rising edge signal, causing capacitor C33 to discharge. During the discharge process, the control chip IC1 synchronously outputs a pulse signal at the zero-crossing point F. In this pulse window, the rising edge (rising edge or falling edge) output by the control chip IC1 triggers the optocoupler module U8 through the AC-passing and DC-blocking characteristics of capacitor C33. Capacitor C33 only turns on the optocoupler module U8 when the rising edge signal arrives and the zero-crossing point F is synchronized. After the optocoupler module U8 is turned on, it provides trigger current to the control electrode K of the thyristor T1. The thyristor T1 is turned on, and the heating wire H1 is energized and heated, forming a circuit.

[0053] The innovation of this invention lies in the series connection of capacitor C33 at the input terminal of optocoupler module U8. By utilizing the characteristic of capacitors to pass AC and block DC, the fixed level output of control chip IC1 is blocked, ensuring that optocoupler module U8 only responds to the transition edge signal. Even if control chip IC1 malfunctions and continuously outputs a high or low level, optocoupler module U8 will not conduct, thus completely eliminating the risk of continuous power supply to the load.

[0054] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style of the specification is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other implementations that can be understood by those skilled in the art.

[0055] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A load control circuit, characterized in that, The device includes a discharge circuit (1), an optocoupler module U8, and a heating circuit (2). The heating circuit (2) includes a live wire ACL, a neutral wire ACN, a thyristor T1, and a heating wire H1. The anode A of the thyristor T1 is connected to the heating wire H1, and the cathode C is connected to the neutral wire ACN. The other end of the heating wire H1 is connected to the live wire ACL. The discharge circuit (1) includes a capacitor C33 and a resistor R15. One end of the capacitor C33 is connected to the control chip IC1, and the other end is connected to the resistor R15. The other end of the resistor R15 is connected to pin 1 of the optocoupler module. Pin 2 of the optocoupler module U8 is grounded, and pin 3 is connected to the control electrode K of the thyristor T1. When the control chip IC1 detects the zero-crossing F signal, it sends a transition edge signal. The capacitor C33 discharges. During the discharge process, the control chip IC1 outputs a pulse signal and generates a zero-crossing F signal, which makes the optocoupler module U8 conduct, and then conducts the thyristor T1 so that the heating circuit (2) forms a loop and works to generate heat.

2. The load control circuit according to claim 1, characterized in that, The discharge time of capacitor C33 is a constant τ, where τ = R15 × C33, R15 is the resistance of resistor C1, and C33 is the capacitance of capacitor C33.

3. The load control circuit according to claim 2, characterized in that, The discharge time constant τ satisfies: τ < half a mains power cycle.

4. The load control circuit according to claim 3, characterized in that, The conduction time t3 of the thyristor T1 is at least partially after the zero-crossing point F, and t3 < τ.

5. The load control circuit according to claim 4, characterized in that, After the control chip IC1 detects the zero-crossing point F, it outputs the transition edge signal after a delay time t1. The delay time t1 satisfies the following condition: t1 ≤ half a mains power cycle.

6. The load control circuit according to claim 5, characterized in that, The delay time t1 plus the discharge time τ must be greater than half a mains power cycle, that is, t1+τ> half a mains power cycle.

7. The load control circuit according to claim 1, characterized in that, The control chip IC1 outputs a pulse signal that is basically synchronized with the zero-crossing point F signal.

8. The load control circuit according to claim 4, characterized in that, The thyristor T1 is a bidirectional thyristor.

9. The load control circuit according to claim 8, characterized in that, It also includes resistor R19, one end of which is connected to pin 4 of the optocoupler module U8, and the other end is connected between the heating wire H1 and the anode A of the thyristor T1.

10. The load control circuit according to claim 1, characterized in that, It also includes resistor R32, which together with capacitor C33 form a charging circuit (3). One end of resistor R32 is grounded to GND, and the other end is connected to capacitor C33.

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