Light source and mainboard driving circuit of projector

Abstract

The utility model discloses a light source and mainboard driving circuit of a projector, which comprises a rectification circuit, a light source driving circuit, a mainboard driving circuit and an isolation transmission element, the light source driving circuit is a non-isolation power supply, the mainboard driving circuit is an isolation power supply, and the mainboard driving circuit controls the working state of the light source driving circuit through the isolation transmission element. According to the utility model, the safety of the mainboard and the I / O port of the projector is ensured, the high efficiency of the light source driving circuit is also considered, and the power adapter is a low-cost and high-efficiency power adapter design scheme, and is suitable for household LED projectors and similar electrical products.

Description

Technical Field

[0001] The utility model relates to a projection device, in particular to a light source and a mainboard driving circuit of a projector. Background Art

[0002] Projectors contain light source driver circuits and motherboard driver circuits. To ensure the safety of the projector's motherboard and I / O ports, current projectors use isolated power supply designs for both the light source driver circuit and the motherboard driver circuit (i.e., the input and output terminals do not share a common ground). As we all know, isolated power supplies generally require isolation components such as transformers. While they offer high stability and safety, the need for these isolation components leads to relatively high hardware costs. Furthermore, due to energy conversion and transmission losses, their efficiency is lower than that of non-isolated power supplies. Conversely, non-isolated power supplies (i.e., the input and output terminals share a common ground) are less secure, but they do not require isolation components such as transformers, resulting in relatively lower hardware costs. Furthermore, due to the lack of energy conversion and transmission losses, their efficiency is also higher.

[0003] Obviously, in the prior art, both the light source driving circuit and the mainboard driving circuit of the projector adopt an isolated power supply design, which improves safety but also sacrifices efficiency. Utility Model Content

[0004] In order to overcome the deficiencies of the prior art, the utility model provides a light source and a mainboard driving circuit for a projector that take both safety and efficiency into consideration.

[0005] The technical solution adopted by the utility model to solve its technical problems is:

[0006] A light source and mainboard driving circuit for a projector, comprising:

[0007] Rectifier circuit: The input end is connected to the live wire ACL and the neutral wire ACN of the mains power, and the output end is the positive pole DC+ of the DC power supply and the reference ground GND1.

[0008] The light source driving circuit is a non-isolated power supply, the input end of which is connected to the output end of the DC power supply, the output end of which is connected to the projector light source LED, and has a light source driving control end.

[0009] Mainboard driving circuit: It is an isolated power supply, including an isolated conversion element. The primary side of the isolated conversion element is connected to the isolated power supply control circuit and the output end of the DC power supply, and the secondary side is the positive output end of the isolated power supply and the reference ground GND2 to power the projector mainboard.

[0010] Isolation transmission element: the positive pole of the input end is connected to the control signal output end EN of the projector mainboard, the negative pole is connected to the reference ground GND2 of the isolation power supply, the positive pole of the output is connected to the light source drive control end, and the negative pole is connected to the reference ground GND1.

[0011] As a further improvement of the present invention, the reference ground GND1 and the reference ground GND2 are isolated by a capacitor CY1.

[0012] As a further improvement of the present invention, the isolation transmission element is connected to the light source driving control end via a field effect transistor Q1.

[0013] As a further improvement of the present invention, the light source driving circuit includes a constant current driving chip U2, and the light source driving control end is a control input end of the constant current driving chip U2.

[0014] As a further improvement of the present invention, the isolation conversion element is a transformer T1, the primary side of the transformer T1 has a primary winding and a feedback winding, and the secondary side has a secondary winding, one end of the primary winding is connected to the positive pole DC+ of the DC power supply, and the other end is connected to the output end of the isolated power supply control circuit, one end of the feedback winding is a feedback voltage end connected to the feedback voltage input end of the isolated power supply control circuit, and the other end is connected to the reference ground GND1; one end of the secondary winding is the positive output end of the isolated power supply, and the other end is the reference ground GND2.

[0015] As a further improvement of the present invention, the isolated power supply control circuit includes a primary-side feedback switching power supply chip U1 , and a feedback voltage input terminal of the primary-side feedback switching power supply chip U1 is connected to the feedback voltage terminal.

[0016] As a further improvement of the present invention, the isolation transmission element is a photocoupler IC1 , and a voltage stabilizing diode ZD1 is connected between the positive electrode of the output end of the photocoupler IC1 and the reference ground GND1 .

[0017] As a further improvement of the present invention, the rectifier circuit includes a rectifier bridge DB1, the input end of the rectifier bridge DB1 is connected to the live wire ACL and the neutral wire CAN of the mains, the output end is the positive pole DC+ of the DC power supply and the reference ground GND1, a varistor MOV1 is connected between the live wire ACL and the neutral wire CAN, a fuse F1 is connected in series to the live wire ACL, a thermistor NTC1 is connected in series to the neutral wire CAN, and a polarity capacitor C4 is connected between the positive pole DC+ and the reference ground GND1.

[0018] As a further improvement of the present invention, a filter circuit C5R12 composed of a polarity capacitor C5 and a resistor R12 connected in parallel is connected between the output ends of the light source driving circuit.

[0019] As a further improvement of the present invention, a filter circuit C1R1 composed of a polar capacitor C1 and a resistor R1 connected in parallel is connected between the output ends of the mainboard drive circuit.

[0020] The beneficial effects of the present invention are as follows: the light source driving circuit of the present invention is a non-isolated power supply, the mainboard driving circuit is an isolated power supply, and the mainboard driving circuit controls the working state of the light source driving circuit through an isolated transmission element, thereby ensuring the safety of the mainboard and I / O port of the projector while taking into account the high efficiency of the light source driving circuit. The present invention is a low-cost, high-efficiency power adapter design solution suitable for home LED projectors and similar electrical appliances. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] Figure 1 It is a schematic diagram of the principle of the present utility model.

[0023] Figure 2 It is a circuit principle diagram of the utility model. DETAILED DESCRIPTION

[0024] Reference Figure 1 A light source and mainboard driving circuit of a projector includes a rectifier circuit, a light source driving circuit, a mainboard driving circuit and an isolation transmission element. The rectifier circuit converts AC power into high-voltage DC power. The high-voltage DC power output end is the positive pole DC+ of the DC power supply and the reference ground GND1, which is the negative pole DC- of the DC power supply.

[0025] The light source driver circuit uses a non-isolated power supply, with a common ground for the input and output. The mainboard driver circuit uses an isolated power supply, with separate grounds for the input and output. The projector's LED light source has no external circuitry, so safety considerations are not necessary. Therefore, a highly efficient, transformer-free, non-isolated power supply is used. The projector mainboard has numerous external I / O ports, requiring an isolated power supply to ensure the safety of the mainboard and I / O ports. The projector mainboard outputs a control signal, EN, to the isolation transmission element, which controls the operating state of the light source driver circuit. The isolation transmission element is electrically and physically isolated, providing excellent isolation and protection.

[0026] Reference Figure 2 , Figure 2 This is a typical circuit schematic diagram given in this embodiment. The circuit includes a rectifier circuit, a light source driving circuit, a mainboard driving circuit and an isolation transmission element. The isolation transmission element uses a photocoupler IC1, and the photocoupler IC1 is connected to the light source driving control terminal through a field effect transistor Q1.

[0027] In this embodiment, the light source driver circuit uses a constant current driver chip U2. The constant current driver chip U2 adopts the SIC953XC series chip, such as the SIC9537CD, SIC9536CD, SIC9534CS, etc. This series of chips is a high-precision LED constant current driver chip with ultra-low system cost. It is suitable for low-power non-isolated step-down LED lighting with a full voltage range of 85V to 265V. It has built-in high-precision sampling and compensation circuits, which enable the circuit to achieve a constant current accuracy of less than ±5%, and can realize the adaptive adjustment of the output current to the inductor and output voltage, thereby achieving excellent line regulation and load regulation. It also integrates a 500V power MOSFET internally, eliminating the need for a secondary feedback circuit or compensation circuit. In addition, the precise and stable adaptive technology makes the system peripheral structure very simple. It can achieve high-precision constant current control with a small number of peripheral components and a wide parameter range, greatly saving system cost and volume. The pin definitions of the SIC953XC series chip are as follows: 1-pin GND, chip ground; 2-pin RADJ, output OVP adjustment pin, an external resistor to GND can continuously adjust the OVP point. When the RADJ pin voltage is <150mV, the system is shut down; 3-pin NC, open pin; 4-pin HV, internal power supply pin, connected to the bus voltage; 5-pin DRN, drain of the internal MOSFET; 6-pin DRN, open pin; 7-pin ISEN, current sampling, an external resistor to ground.

[0028] In this embodiment, the isolation conversion element is transformer T1, and the isolated power supply control circuit utilizes a primary-side feedback switching power supply chip U1. This primary-side feedback switching power supply chip U1 utilizes the FM3783 series, such as the FM3783HA, FM3783BA, and FM3783AA. This series of chips is a low-power primary-side feedback (PSR) switching power supply chip with integrated high-power BJT transistors, suitable for isolated, high-efficiency, low-power portable device charger applications. The FM3783 series chips utilize unique primary-side feedback control technology with constant current and voltage capabilities, as well as unique light-load frequency modulation technology to reduce the chip's own power consumption under light loads, enabling efficient applications. The FM3783 series chips also feature output line loss compensation technology to ensure sufficient output power at high currents. The pin definitions of the FM3783 series chips are: pin 1 FB, feedback voltage input; pin 2 CS, current sampling resistor connected between CS and GND; pin 3 VCC, internal power bypass capacitor connected between VCC and GND; pin 4 E, emitter of built-in high-power BJT tube; pin 5 / pin 6 C, collector of built-in high-power BJT tube; pin 7 GND, chip ground.

[0029] The rectifier circuit includes a rectifier bridge DB1. Its input terminals are connected to the mains power line (ACL) and neutral line (CAN). Its output terminals are connected to the DC power supply's positive electrode (DC+) and reference ground (GND1). A varistor (MOV1) is connected between the ACL and neutral lines (CAN). A fuse (F1) is connected in series with the ACL, and a thermistor (NTC1) is connected in series with the neutral line (CAN). A polarized capacitor (C4) is connected between the DC+ and reference ground (GND1). The rectifier circuit converts AC mains power into high-voltage DC power.

[0030] The light source driving circuit includes a constant current driving chip U2, the first pin of the constant current driving chip U2 is connected to the reference ground GND1 of the DC power supply; the second pin of the constant current driving chip U2 is connected to the drain of the field effect transistor Q1, and a resistor R15 is connected between the drain and source of the field effect transistor Q1, and the gate of the field effect transistor Q1 is connected to the positive pole of the projector light source LED through a resistor R11 and an electron R13; the fourth pin of the constant current driving chip U2 is connected to the positive pole DC+ of the DC power supply, and a resistor R14 is connected between the fourth pin and the positive pole DC+ of the DC power supply; the fifth pin of the constant current driving chip U2 is connected to the negative pole of the projector light source LED through an inductor L1; the sixth pin of the constant current driving chip U2 is a free pin, and a Zener diode D7 and a Zener diode D8 are connected in parallel between the fourth pin, the fifth pin and the sixth pin; a resistor R16 and a resistor R17 are connected in parallel between the seventh pin and the first pin of the constant current driving chip U2. A filter circuit C5R12 composed of a polarity capacitor C5 and a resistor R12 connected in parallel is connected between the output ends of the light source driving circuit.

[0031] The motherboard drive circuit includes a transformer T1 and a primary-side feedback switching power supply chip U1. The primary side of the transformer T1 has a primary winding (i.e., pins 1 and 2) and a feedback winding (i.e., pins 3 and 4), and the secondary side has a secondary winding (i.e., pins 5 and 6). Pin 1 of the transformer T1 is connected to the positive electrode DC+ of the DC power supply, and pin 3 of the transformer T1 is connected to the reference ground GND1; pin 6 of the transformer T1 outputs a positive electrode VOUT+ through a voltage-stabilizing diode D2, and pin 5 of the transformer T1 outputs a negative electrode VOUT-. The positive electrode VOUT+ and the negative electrode VOUT- are used to power the projector motherboard. A resistor R7 is connected between pin 1 of the primary-side feedback switching power supply chip U1 and pin 4 of the transformer T1. Current sampling resistors R8 and R9 are connected between pins 2 and 7 of the primary-side feedback switching power supply chip U1. Pin 3 of the primary-side feedback switching power supply chip U1 is connected to the DC+ positive terminal of the DC power supply via resistors R5 and R2. Pin 3 is connected to the reference ground GND1 via a polarized capacitor C3 and to pin 4 of the transformer T1 via a zener diode D6. Pins 5 and 6 of the primary-side feedback switching power supply chip U1 are connected to pin 2 of the transformer T1. A filter circuit C1R1, consisting of a polarized capacitor C1 and a resistor R1 in parallel, is connected between the output terminals of the mainboard drive circuit. Transformer T1 converts high-voltage DC power to low-voltage DC power to power the projector mainboard and provides constant current and voltage functions, ensuring the safety of the projector mainboard and I / O ports.

[0032] The isolation transmission element includes a photocoupler IC1 and a field-effect transistor Q1. A voltage-stabilizing diode ZD1 is connected between the positive output terminal of the photocoupler IC1 and the reference ground GND1. The first pin of the photocoupler IC1 is connected to the control signal EN via a resistor R4. The second pin of the photocoupler IC1 is connected to the reference ground GND1 via a resistor R10. The third pin of the photocoupler IC1 and the source of the field-effect transistor Q1 are connected to the reference ground GND1. The fourth pin of the photocoupler IC1 is connected to the gate of the field-effect transistor Q1. A voltage-stabilizing diode ZD1 is connected between the third and fourth pins of the photocoupler IC1. The gate of the field-effect transistor Q1 is connected to the positive electrode DC+ of a DC power supply via resistors R11 and R13.

[0033] Working Principle: The AC mains live wire (ACL) and neutral wire (CAN) are fed into a rectifier circuit, which converts the AC power into high-voltage DC. This DC power is split into two paths: one path powers the projector mainboard through the isolated power supply's mainboard driver circuit, and the other path powers the projector's LED light source through the non-isolated power supply's light source driver circuit. The mainboard driver circuit controls the light source driver circuit's operating state via an isolation transmission element. This isolation transmission element uses an optocoupler IC1 as a physical isolation device. Pin 2 (the OVP adjustment pin) of the constant current driver chip U2, which has a low-level cutoff characteristic, is grounded via a field-effect transistor (FET) Q1. When powered on, FET Q1 is on, and the voltage at pin 2 of the constant current driver chip U2 is close to zero volts, effectively deactivating the constant current driver chip U2, ensuring shutdown control. When the projector mainboard outputs a high-level control signal EN (which can be a PWM signal), the optocoupler IC1 is turned on. At this time, the voltage across the field-effect tube Q1 is lower than the conduction voltage, the field-effect tube Q1 is cut off, and the voltage of the second pin of the constant-current driver chip U2 rises back to above 0.15V. The constant-current driver chip U2 enters the working startup state, thereby driving the projector light source LED to light up.

[0034] The above implementation methods cannot limit the protection scope of the present invention. Equal modifications and changes made by those skilled in the art without departing from the overall concept of the present invention are still within the scope of the present invention.

Claims

1. A light source and mainboard driving circuit for a projector, characterized in that: include: Rectifier circuit: The input end is connected to the live wire ACL and the neutral wire ACN of the mains power supply, and the output end is the positive pole DC+ of the DC power supply and the reference ground GND1; Light source driving circuit: a non-isolated power supply, the input end of which is connected to the output end of the DC power supply, the output end of which is connected to the projector light source LED, and has a light source driving control end; Mainboard drive circuit: It is an isolated power supply, including an isolated conversion element. The primary side of the isolated conversion element is connected to the isolated power control circuit and the output end of the DC power supply. The secondary side is the positive output end of the isolated power supply and the reference ground GND2 to power the projector mainboard; Isolation transmission element: the positive pole of the input end is connected to the control signal output end EN of the projector mainboard, the negative pole is connected to the reference ground GND2 of the isolation power supply, the positive pole of the output is connected to the light source drive control end, and the negative pole is connected to the reference ground GND1.

2. The light source and mainboard driving circuit of the projector according to claim 1, characterized in that The reference ground GND1 and the reference ground GND2 are isolated from each other by a capacitor CY1.

3. The light source and mainboard driving circuit of the projector according to claim 1, characterized in that The isolation transmission element is connected to the light source driving control terminal through the field effect transistor Q1.

4. The light source and mainboard driving circuit of the projector according to claim 1, characterized in that The light source driving circuit includes a constant current driving chip U2 , and the light source driving control terminal is a control input terminal of the constant current driving chip U2 .

5. The light source and mainboard driving circuit of the projector according to claim 1, characterized in that The isolation conversion element is a transformer T1, the primary side of the transformer T1 has a primary winding and a feedback winding, and the secondary side has a secondary winding. One end of the primary winding is connected to the positive pole DC+ of the DC power supply, and the other end is connected to the output end of the isolated power supply control circuit. One end of the feedback winding is a feedback voltage end connected to the feedback voltage input end of the isolated power supply control circuit, and the other end is connected to the reference ground GND1; one end of the secondary winding is the positive output end of the isolated power supply, and the other end is the reference ground GND2.

6. The light source and mainboard driving circuit of the projector according to claim 5, characterized in that The isolated power supply control circuit includes a primary-side feedback switching power supply chip U1 , and a feedback voltage input terminal of the primary-side feedback switching power supply chip U1 is connected to the feedback voltage terminal.

7. The light source and mainboard driving circuit of the projector according to claim 1, characterized in that The isolation transmission element is a photocoupler IC1 , and a voltage stabilizing diode ZD1 is connected between the positive electrode of the output end of the photocoupler IC1 and the reference ground GND1 .

8. The light source and mainboard driving circuit of the projector according to claim 1, characterized in that The rectifier circuit includes a rectifier bridge DB1, the input end of the rectifier bridge DB1 is connected to the live wire ACL and the neutral wire CAN of the mains power, and the output end is the positive electrode DC+ of the DC power supply and the reference ground GND1. A varistor MOV1 is connected between the live wire ACL and the neutral wire CAN, a fuse F1 is connected in series to the live wire ACL, a thermistor NTC1 is connected in series to the neutral wire CAN, and a polarity capacitor C4 is connected between the positive electrode DC+ and the reference ground GND1.

9. The light source and mainboard driving circuit of the projector according to claim 1, characterized in that A filter circuit C5R12 composed of a polarity capacitor C5 and a resistor R12 connected in parallel is connected between the output ends of the light source driving circuit.

10. The light source and mainboard driving circuit of the projector according to claim 1, characterized in that A filter circuit C1R1 composed of a polarity capacitor C1 and a resistor R1 connected in parallel is connected between the output ends of the mainboard driving circuit.

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