WO2017097002A1

WO2017097002A1 - Anti-surge switching power supply and anti-surge circuit

Info

Publication number: WO2017097002A1
Application number: PCT/CN2016/099354
Authority: WO
Inventors: 王合球; 郝留全
Original assignee: 深圳欧陆通电子有限公司
Priority date: 2015-12-09
Filing date: 2016-09-19
Publication date: 2017-06-15
Also published as: CN105429449A; CN105429449B

Abstract

An anti-surge switching power supply comprises an alternating-current input circuit (100), a rectification circuit (200), a voltage transformation circuit (400), an output circuit (500), a control circuit (600), and an anti-surge circuit (300). The alternating-current input circuit (100) is connected to an input end of the rectification circuit (200). An output end of the rectification circuit (200) is connected to the anti-surge circuit (300). An output end positive electrode of the rectification circuit (200) is connected to an input end of the voltage transformation circuit (400). The anti-surge circuit (300) is connected to the control circuit (600). An output end of the voltage transformation circuit (400) is connected to an input end of the output circuit (500). The control circuit (600) outputs control signals to the anti-surge circuit (300), and the control signals comprise a first control signal and a second control signal. When the anti-surge circuit (300) receives the first control signal generated by the control circuit (600), the generation of an anti-surge current is prevented. The anti-surge switching power supply can effectively reduce a surge current in a switch-on process of the switching power supply, thereby improving the reliability of a device.

Description

Anti-surge power supply and anti-surge circuit

[0001] The present invention relates to the field of power supply, and more particularly to an anti-surge power supply and surge protection circuit.

Background technique

[0002] Shaoguan power supply has the advantages of small size and high efficiency, and is widely used in computer, industrial control, communication and consumer electronics.

[0003] In the prior art, the input end of the power supply is usually provided with a high voltage electrolytic capacitor, which is used as a smooth input voltage and a saving energy. When the power is turned off, due to the instantaneous conductivity of the capacitor, the equivalent resistance at both ends of the electrolytic capacitor is approximately 0 Ω. The current flowing through the main loop has several tens of amps. In particular, after the capacitor is increased, the inrush current of this crucible is larger. Such a large inrush current at the moment of power-on can cause the input fuse to blow or the electric shock to be burned out, or the rectifier bridge overcurrent damage, resulting in the malfunction of the power supply.

[0004] To solve this problem, the current conventional practice is to reduce the inrush current by connecting NTC (thermistor) in series with the input. However, when the circuit works normally, the resistor will always work, which will cause its own temperature to rise. As the internal temperature of the power supply increases, the NTC resistance decreases, and the inrush current increases, making the device safe and reliable. Low sex.

technical problem

[0005] The current practice is to reduce the inrush current by connecting NTC (thermistor) in series with the input. However, when the circuit works normally, the resistor will always work, which will cause its own temperature to rise. As the internal temperature of the power supply increases, the NTC resistance decreases, and the inrush current increases, making the device safe and reliable. Low problem solution

Technical solution

[0006] The technical problem to be solved by the present invention is to provide a surge-proof power supply and a surge-proof circuit against the above-mentioned short-circuit surge current of the prior art. [0007] The technical solution adopted by the present invention to solve the technical problem thereof is: constructing a surge-proof power supply.

[0008] comprising an AC input circuit, a rectifier circuit, a transformer circuit, an output circuit, and a control circuit, wherein the power supply further includes an anti-surge circuit;

[0009] The AC input circuit is connected to an input end of the rectifier circuit, an output end of the rectifier circuit is connected to the anti-surge circuit, and an output terminal of the rectifier circuit is connected to an input end of the transformer circuit, The anti-surge circuit is connected to the control circuit, and the output end of the transformer circuit is connected to the input end of the output circuit

[0010] the control circuit outputs a control signal to the anti-surge circuit, and the control signal includes a first control signal and a second control signal;

[0011] when the anti-surge circuit receives the first control signal generated by the control circuit, the anti-surge circuit enters a first working state to prevent generation of a surge current;

[0012] when the anti-surge circuit receives the second control signal generated by the control circuit, the anti-surge circuit enters a second working state, and the anti-surge power supply enters a normal operation. status.

[0013] In the surge protection power supply of the present invention, when the AC input circuit is turned on, the control circuit generates a first control signal during the self-starting process;

[0014] after the AC input circuit is turned on, the control circuit generates a second control signal after self-starting is completed.

[0015] In the anti-surge power supply of the present invention, the anti-surge circuit includes: a field effect transistor Q3 08, a resistor R310, a capacitor C311, a matching circuit, wherein: the field effect transistor The drain of the Q308 is connected to the anode of the output of the rectifier circuit through a capacitor C309, the source of the FET Q308 is grounded, and the two ends of the resistor R310 are respectively connected to the drain and the source of the FET Q308. The two ends of the capacitor C311 are respectively connected to the drain and the source of the FET Q308, and the gate of the FET Q308 is connected to the control circuit through the matching circuit.

[0016] in the first working state, the control circuit outputs the first control signal to the anti-surge circuit, and the matching circuit cannot provide the FET Q308 turn-on voltage, the FET Q308 is not turned on, and the current output by the rectifier circuit is turned on by the capacitor C309, the resistor R310, and the capacitor C311;

[0017] in the second working state, the control circuit outputs the second control signal to the anti-surge circuit, the matching circuit provides a FET Q308 turn-on voltage, the FET Q308 Turn on. [0018] In the anti-surge power supply of the present invention, the matching circuit includes: a resistor R301, a diode D302, a capacitor C303, a resistor R304, a transistor Q305, a Zener diode ZD306, and a resistor R307, wherein: The gate of the FET Q308 is grounded through the resistor R307, the gate of the FET Q308 is connected to the emitter of the transistor Q305, and the base of the transistor Q305 is connected to the cathode of the Zener diode ZD306. The positive pole of the Zener diode ZD306 is grounded, the two ends of the resistor R304 are respectively connected to the base and the collector of the transistor Q305, and the collector of the transistor Q305 is grounded through the capacitor C3 03, and the transistor Q305 is The collector is connected to one end of the resistor R301, the other end of the resistor R301 is connected to the cathode of the diode D302, and the anode of the diode D302 is connected to the control circuit, wherein:

[0019] The control circuit 600 outputs a second control signal to the resistor R301 via the diode D302, and the resistor R301, the capacitor C303, and the resistor R304 provide a driving voltage for the transistor Q305 to turn on the Q305. Resistor R307 discharges the field effect transistor Q308 after it is not operating.

[0020] In the first operating state, a maximum current value of the main circuit of the surge-proof power supply is a ratio of an output voltage of the rectifier circuit to the resistor R310.

[0021] Preferably, the resistance R310 has a resistance of 20 Ω, and the capacitance C311 is 1000 PF.

[0022] Preferably, the control circuit comprises a microcontroller capable of emitting a pulse width modulation control signal.

[0023] In addition, the present invention also constructs an anti-surge circuit, including: a field effect transistor Q308, a resistor R310, a capacitor C 311, a matching circuit, wherein: the drain of the FET Q308 is connected through the capacitor C309 The output terminal of the rectifier circuit is positive, the source of the FET Q308 is grounded, and the two ends of the resistor R310 are respectively connected to the drain and the source of the FET Q308, and the two ends of the capacitor C311 are respectively connected The drain and source of the FET Q308 are described, and the gate of the FET Q308 receives a control signal through the matching circuit.

[0024] In the anti-surge circuit of the present invention, the matching circuit includes: a resistor R301, a diode D302, a capacitor C303, a resistor R304, a transistor Q305, a Zener diode ZD306, and a resistor R307, wherein: the field effect The gate of the transistor Q308 is grounded through the resistor R307, the gate of the FET Q308 is connected to the emitter of the transistor Q305, and the base of the transistor Q305 is connected to the cathode of the Zener diode ZD30 6 The positive pole of the Zener diode ZD306 is grounded, and the two ends of the resistor R304 are respectively connected to the base and the collector of the transistor Q305, and the collector of the transistor Q305 is connected through the capacitor C303. The collector of the transistor Q305 is connected to one end of the resistor R301, the other end of the resistor R301 is connected to the cathode of the diode D302, and the anode of the diode D302 receives a control signal.

[0025] In the anti-surge circuit of the present invention, the control signal includes a first control signal and a second control signal, wherein:

[0026] The input control signal is a first control signal 吋, the matching circuit cannot provide the FET Q3 08 turn-on voltage, the FET Q308 is not turned on, and the current output by the rectifier circuit passes The capacitor C309, the resistor R310, and the capacitor C311 are turned on;

[0027] The input control signal is a second control signal 吋, the matching circuit provides a voltage of the FET Q308, and the FET Q308 is turned on.

Advantageous effects of the invention

Beneficial effect

[0028] The implementation of the present invention has the following beneficial effects: During the power-on process of the switch, the first control signal is generated by the control circuit, and the anti-surge circuit is controlled to enter the first working state to prevent the generation of the inrush current, which can be effectively reduced. Small inrush currents improve equipment reliability.

Brief description of the drawing

DRAWINGS

[0029] The present invention will be further described below in conjunction with the accompanying drawings and embodiments, in which:

1 is a circuit diagram of a surge-proof power supply of the present invention;

2 is a circuit diagram of the matching circuit shown in FIG. 1;

3 is a waveform diagram of a surge current of the unsurfacing circuit 300;

4 is a waveform diagram of a surge current of the surge prevention circuit 300.

BEST MODE FOR CARRYING OUT THE INVENTION

The technical solutions in the embodiments of the present invention are clearly and completely described in the following with reference to the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. example. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without departing from the inventive scope are the scope of the present invention. [0035] As shown in FIG. 1, the present invention discloses a surge-proof power supply, including an AC input circuit 100, a rectifier circuit 200, an anti-surge circuit 300, a transformer circuit 400, an output circuit 500, and control. The circuit 600; wherein, the AC input circuit 100 is connected to the input end of the rectifier circuit 200, the output end of the rectifier circuit 200 is connected to the anti-surge circuit 300, and the output terminal of the rectifier circuit 200 is connected to the input end of the transformer circuit 400, and the anti-surge circuit 300 is connected to the control circuit 600, and the output of the transformer circuit 400 is connected to the input end of the output circuit 500.

[0036] The AC input circuit 100 is a current input end of the surge-proof power supply, and is connected to an external AC power source to provide an AC input for the power supply. The AC input circuit 100 further includes an insurance arrester and a varistor.

Devices such as thermistors, common-mode inductors, and resistors provide a starting current for the control circuit 600 during the downtime.

[0037] Capacitor C309 can be a high-voltage electrolytic capacitor C309, which functions as a smooth input voltage and saves energy. However, at the instant of the power-off of the power supply, the equivalent resistance of the capacitor C309 is approximately 0 Ω due to the instantaneous conductivity of the capacitor. Therefore, the current in the main circuit of the power supply is up to several amperes and the device is damaged. Therefore, the present invention provides an anti-surge circuit 300 between the capacitor C3 09 and the control circuit 600 and the rectifier circuit 200, which can be effective during the downtime process. Reduce the generation of inrush current and protect the power supply.

[0038] The working principle of the surge-proof power supply is: the control circuit 600 outputs a control signal to the anti-surge circuit 300, and the control signal includes a first control signal and a second control signal;

[0039] When the AC input circuit 100 is turned on, the control circuit 600 generates a first control signal during the self-starting process, and when the anti-surge circuit 300 receives the first control signal generated by the control circuit 600, the anti-surge circuit 300 Enter the first working state to prevent inrush current generation;

[0040] After the AC input circuit 100 is turned on, the control circuit 600 generates a second control signal after the self-starting is completed, and when the anti-surge circuit 300 receives the second control signal generated by the control circuit 600, the anti-surge circuit 300 Entering the second working state, the surge-proof power supply enters the normal working state.

[0041] The FET is connected between the control circuit 600 and the transformer circuit 400. The transformer circuit 400 is connected to the control signal input terminal of the surge protection circuit 300. When the AC input circuit 100 is connected to the AC power, the control circuit 600 is in self-control. During the startup process, the FET has no conduction signal, the 吋 transformer circuit does not generate an induced voltage, the matching circuit 312 cannot provide the conduction voltage of the FET Q308, and the FET Q308 does not operate; when the control circuit 600 completes the startup The FET is turned on, so that the transformer circuit 400 generates an induced voltage, the induced voltage enables the matching circuit 312 to provide the FET Q308 turn-on voltage, and the FET Q308 operates. The source enters the normal operating mode. Therefore, in the same way that the inrush current is reduced, the field effect transistor Q308 can be used for normal operation.

[0042] Further, the anti-surge circuit 300 includes a field effect transistor Q308, a resistor R310, a capacitor C311, and a matching circuit 312, wherein: the drain of the field effect transistor Q308 is connected to the anode of the output terminal of the rectifier circuit 200 through the capacitor C309, and the field effect The source of the transistor Q308 is grounded. The two ends of the resistor R310 are respectively connected to the drain and the source of the FET Q308. The two ends of the capacitor C311 are respectively connected to the drain and the source of the FET Q308, and the gate of the FET Q308. The control circuit 600 is connected through a matching circuit 312.

[0043] The field effect transistor Q308 is an N-channel field effect transistor, or a P-channel field effect transistor, or a bypass transistor. The function of the field effect transistor Q308 is: the control circuit 600 does not conduct during the startup phase during the downtime. The current is turned on through the resistor R310 and the capacitor C311 to protect the circuit; during the downtime, the control circuit 600 is turned on after being turned on, so that the current is turned on through the field effect transistor Q308.

[0044] The specific working principle of the anti-surge circuit 300 is: In the first working state, the control circuit 600 outputs a first control signal to the anti-surge circuit 300, and the matching circuit 312 cannot provide the FET Q308 turn-on voltage, the field The effect transistor Q308 is not turned on, and the current outputted by the rectifier circuit 200 is turned on by the capacitor C309, the resistor R310, and the capacitor C311. The maximum current value of the main circuit of the surge-proof power supply is the output voltage of the rectifier circuit 200 and the resistor R310. Ratio, the size of the resistor R310, capacitor C311 value is adjusted according to the needs of the power supply

[0045] Preferably, the resistance of the resistor R310 is 20 Ω, and the capacitance C311 is 1000 PF.

[0046] In the second operating state, the control circuit 600 outputs a second control signal to the anti-surge circuit 300, the matching circuit 312 provides the FET Q308 turn-on voltage, and the FET Q308 turns on.

Specifically, as shown in FIG. 2, the matching circuit 312 includes: a resistor R301, a diode D302, a capacitor C303, a resistor R304, a transistor Q305, a Zener diode ZD306, and a resistor R307, where: a gate of the field effect transistor Q3 08 The ground of the FET Q308 is connected to the emitter of the transistor Q305 through the resistor R307, the base of the transistor Q305 is connected to the cathode of the Zener diode ZD306, the anode of the Zener diode ZD306 is grounded, and the two ends of the resistor R304 are respectively connected to the transistor Q305. The base and the collector, the collector of the transistor Q305 is grounded through the capacitor C303, the collector of the transistor Q305 is connected to one end of the resistor R301, the other end of the resistor R301 is connected to the cathode of the diode D302, and the anode of the diode D302 is connected to the control circuit 600.

[0048] The control circuit (600) outputs a second control signal through the diode D302 to the resistor R301, the resistor R301, The capacitor C303 and the resistor R304 provide a driving voltage for the transistor Q305 to turn on the Q305, and the resistor R307 discharges the field effect transistor Q308 after it is not working.

[0049] The triode Q305 is a PNP type triode or an NPN type triode.

[0050] The anti-surge power supply of the present invention is compared with the experimental results of the conventional power supply without the anti-surge circuit 300, and the comparison results are shown in FIG. 3 and FIG. 4:

[0051] As shown in FIG. 3, the figure shows a waveform of a surge current of a power supply without a surge protection circuit 300;

[0052] As shown in FIG. 4, the figure shows a surge current waveform of a bypass power supply in the case where the surge protection circuit 300 of the present invention is added;

[0053] It can be seen from the current curve recorded in FIG. 3 that, in the surge-proof circuit 300 of the present invention, the maximum peak value of the surge current is about 60 amps during the power-on process; The current curve recorded in Fig. 4 can be seen. In the anti-surge circuit 300 of the present invention, the maximum peak value of the surge current is about 30.8 amps during the power-on process, indicating the surge protection of the present invention. Circuit 300 has a significant inhibitory effect on the inrush current.

As shown in FIG. 1 , the present invention also constructs an anti-surge circuit, including: a field effect transistor Q308, a resistor R310, a capacitor C311, and a matching circuit 312, wherein: the drain of the field effect transistor Q308 is connected through a capacitor C309. The output terminal of the rectifier circuit 200 is positive, the source of the FET Q308 is grounded, and the two ends of the resistor R310 are respectively connected to the drain and the source of the FET Q308, and the two ends of the capacitor C311 are respectively connected to the drain of the FET Q308 and The source, the gate of the FET Q308 receives the control signal through the matching circuit 312.

[0055] The matching circuit 312 includes: a resistor R301, a diode D302, a capacitor C303, a resistor R304, a transistor Q 305, a Zener diode ZD306, and a resistor R307, wherein: the gate of the field effect transistor Q308 is grounded through a resistor R307, and the field effect transistor Q308 The gate is connected to the emitter of the transistor Q305, the base of the transistor Q305 is connected to the cathode of the Zener diode ZD306, the anode of the Zener diode ZD306 is grounded, and the two ends of the resistor R304 are respectively connected to the base and the collector of the transistor Q305, and the transistor Q305 is The collector is grounded through a capacitor C303, the collector of the transistor Q305 is connected to one end of the resistor R301, the other end of the resistor R301 is connected to the cathode of the diode D302, and the anode of the diode D302 receives a control signal.

[0056] The working principle of the anti-surge circuit is:

[0057] The control signal includes a first control signal and a second control signal, wherein: [0058] The input control signal is the first control signal 吋, and the control circuit 600 outputs the first control signal to the anti-surge circuit 300, the resistor R301, the diode D302, the capacitor C303, the resistor R304, the transistor Q305, the Zener diode ZD306, and the resistor R307. The FET Q308 cannot be turned on, the FET Q308 is not turned on, and the current output by the rectifier circuit 200 is turned on through the capacitor C309, the resistor R310, and the capacitor C311;

[0059] The input control signal is the second control signal 吋, and the control circuit 600 outputs the second control signal to the anti-surge circuit 300, the resistor R301, the diode D302, the capacitor C303, the resistor R304, the transistor Q305, the Zener diode ZD306, and the resistor R307. The FET Q308 is turned on, and the FET Q308 is turned on.

The above embodiments are merely illustrative of the technical concept and the features of the present invention, and the purpose of the present invention is to enable those skilled in the art to understand the contents of the present invention and to implement the present invention without limiting the scope of the present invention. All changes and modifications made within the scope of the claims of the present invention are intended to be included within the scope of the appended claims.

Claims

Claim

[Claim 1] A surge-proof power supply including an AC input circuit (100) and a rectifier circuit (200)

a transformer circuit (400), an output circuit (500), and a control circuit (600), wherein the switching power supply further includes an anti-surge circuit (300); the AC input circuit (100) An input end of the rectifier circuit (200) is connected, an output end of the rectifier circuit (200) is connected to the anti-surge circuit (300), and an output terminal of the rectifier circuit (200) is positively connected to the transformer circuit ( 400) an input, the anti-surge circuit (300) is connected to the control circuit (600), the output end of the transformer circuit (400) is connected to the input end of the output circuit (500);

The control circuit (600) outputs a control signal to the anti-surge circuit (300), the control signal comprising a first control signal and a second control signal;

When the anti-surge circuit (300) receives the first control signal generated by the control circuit (600), the anti-surge circuit (300) enters a first working state to prevent generation of a surge current;

When the anti-surge circuit (300) receives the second control signal generated by the control circuit (600), the anti-surge circuit (300) enters a second working state, the anti-surge The power supply is in normal working condition.

[Claim 2] The surge protection power supply according to claim 1, wherein the control circuit (600) is generated during the self-starting process after the AC input circuit (100) is turned on. The first control signal;

After the AC input circuit (100) is turned "on", the control circuit (600) generates the second control signal after self-starting is completed.

[Claim 3] The surge protection power supply according to claim 1, wherein the surge protection circuit (300) comprises: a field effect transistor Q308, a resistor R310, a capacitor C311, and a matching circuit. (312), wherein: the drain of the FET Q308 is connected to the anode of the output terminal of the rectifier circuit (200) through a capacitor C309, the source of the FET Q308 is grounded, the resistor R310 and the capacitor C311 is connected in parallel between the drain and the source of the FET Q308, and the gate of the FET Q308 is connected through the matching circuit (312) Connected to the control circuit (600),

In the first operating state, the control circuit (600) outputs the first control signal to the anti-surge circuit (300), and the matching circuit (312) cannot provide the FET Q308 turn-on voltage The FET Q308 is not turned on, and the current output by the rectifier circuit (200) is turned on by the capacitor C309, the resistor R310, and the capacitor C311; in the second operating state, the control circuit (600) And outputting the second control signal to the anti-surge circuit (300), the matching circuit (312) provides a FET Q 308 turn-on voltage, and the FET Q308 is turned on.

[Claim 4] The surge protection power supply according to claim 3, wherein the matching circuit (312) comprises: a resistor R301, a diode D302, a capacitor C303, a resistor R304, a transistor Q305, and a voltage regulator. a diode ZD306, a resistor R307, wherein: a gate of the FET Q 308 is grounded through the resistor R307, a gate of the FET Q308 is connected to an emitter of the transistor Q305, and a base of the transistor Q305 Connecting the cathode of the Zener diode ZD306, the anode of the Zener diode ZD306 is grounded, and the two ends of the resistor R304 are respectively connected to the base and the collector of the transistor Q305, and the collector of the transistor Q305 passes through the The capacitor C303 is grounded, the collector of the transistor Q305 is connected to one end of the resistor R301, the other end of the resistor R301 is connected to the cathode of the diode D302, and the anode of the diode D302 is connected to the control circuit (600). : the control circuit (600) outputs a second control signal through the diode D302 to the resistor R301, the resistor R301 The capacitor C303 and the resistor R304 of transistor Q3 05 supplies a driving voltage to the Q305 is turned on, the resistor R307 of the FET Q308 for discharging inch does not work.

[Claim 5] The surge-proof power supply according to claim 3, wherein in the first operating state, a maximum current value of the main circuit of the surge-proof power supply The ratio of the output voltage of the rectifier circuit (200) to the resistor R310.

[Claim 6] The surge-proof power supply according to claim 5, wherein the resistor R3

The resistance of 10 is 20 Ω, and the capacitance C311 is 1000 PF.

[Claim 7] The switching power supply according to claim 1, wherein the control circuit (600) The invention comprises a single chip microcomputer which can issue a pulse width modulation control signal, and the capacitor C309 is a high voltage electrolytic capacitor.

[Claim 8] A surge protection circuit, comprising: a field effect transistor Q308, a resistor R310, a capacitor C311, and a matching circuit (312), wherein: a drain of the field effect transistor Q308 is connected through a capacitor C309 The output terminal of the rectifier circuit (200) is positive, the source of the FET Q3 08 is grounded, and the two ends of the resistor R310 are respectively connected to the drain and the source of the FET Q308, and the capacitor C311 The two ends are respectively connected to the drain and the source of the FET Q308, and the gate of the FET Q308 receives the control signal through the matching circuit (312).

[Claim 9] The surge protection circuit according to claim 8, wherein the matching circuit (312)

The method includes: a resistor R301, a diode D302, a capacitor C303, a resistor R304, a transistor Q3 05, a Zener diode ZD306, and a resistor R307, wherein: a gate of the FET Q308 is grounded through the resistor R307, the FET The gate of the Q308 is connected to the emitter of the transistor Q305, the base of the transistor Q305 is connected to the cathode of the Zener diode ZD306, the anode of the Zener diode ZD306 is grounded, and the two ends of the resistor R304 are respectively connected. The base and the collector of the transistor Q305, the collector of the transistor Q305 is grounded through the capacitor C303, the collector of the transistor Q305 is connected to one end of the resistor R301, and the other end of the resistor R301 is connected The cathode of diode D302, the anode of diode D302 receives a control signal.

[Claim 10] The anti-surge circuit according to claim 9, wherein the control signal comprises a first control signal and a second control signal, wherein:

The input control signal is a first control signal 吋, the matching circuit (312) cannot provide the FET Q308 turn-on voltage, the FET Q308 is not turned on, and the rectifier circuit (200) outputs a current is conducted through the capacitor C309, the resistor R310, and the capacitor C311;

The input control signal is a second control signal 吋, the matching circuit (312) provides a turn-on voltage of the FET Q308, and the FET Q308 is turned on.