A rectifier bridge starting protection circuit

Abstract

The present invention discloses a rectifier bridge startup protection circuit. The protection circuit includes a rectifier bridge, an energy storage capacitor C0, and a power resistor R1. The AC power supply charges the capacitor C0 through the power resistor R1 and the rectifier bridge. The power resistor R1 is connected in series on the loop between the AC power supply and the rectifier bridge. The energy storage capacitor C0 is connected across the rectifier bridge. It includes an IC control chip, an NMOS transistor N1, an NOMS transistor N2, a capacitor C1, a capacitor C2, an HB pin, an HO pin, and an HS pin. The gates of the NMOS transistor N1 and the NOMS transistor N2 are connected to both ends of the power resistor R1. The sources and drains of the NMOS transistor N1 and the NOMS transistor N2 are connected respectively. The circuit structure of the present invention is simple. Only one power resistor, two power NMOS transistors, and one control IC are needed to achieve the solution. The present invention limits the startup peak current of the AC power supply, protects the safety of the rectifier bridge, and ensures that the device can start normally under high and low temperature conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of power circuits, and particularly to a rectifier bridge startup protection circuit. Background Art

[0002] Devices powered by direct current usually obtain power from an AC power supply network through a diode rectifier bridge. The circuit structure of the rectifier bridge is as Figure 1 shown. When the device is powered on with the AC input voltage at its maximum value, the peak voltage value at the two output terminals of the AC power supply is Vac * 1.414. At this time, the internal power supply device has not started yet, and the voltage difference across the energy storage capacitor C0 is 0V. Therefore, the peak voltage of the AC power supply is completely borne by the two series-connected diodes and the loop parasitic resistance r. Usually, the resistance value of the resistance r is very small, only a few ohms. Ignoring the voltage drops of the two diodes, the startup peak current of the AC power supply is obtained as:

[0003] Ipeak = Vac * 1.414 / r

[0004] This peak current is very large and may cause damage to the rectifier bridge, connecting wires, and other components.

[0005] Currently, the common solution is to add an NTC resistor (negative temperature coefficient resistor), as Figure 2 shown. The resistance value of the NTC resistor decreases with the increase in temperature. For example, if we use a 100Ω NTC resistor, its resistance value at room temperature of 25°C is 100Ω, and the startup peak current of the rectifier bridge is approximately limited to Vac * 1.414 / 100, thus ensuring the safety of the rectifier bridge components. When the power supply device is working normally, the current flows through the NTC resistor and makes it heat up. When the temperature rises to 85°C, the resistance value of the NTC resistor drops to approximately 10Ω, reducing the power consumption. This solution has two problems: 1. For high-power devices, although the resistance value of the NTC resistor has decreased when the power supply device is working normally, its power consumption is still very considerable; 2. Under low-temperature conditions, the resistance value of the NTC resistor will increase. For a 100Ω NTC resistor, its resistance value at -40°C is approximately 34 KΩ, which may cause the startup current of the AC power supply to be too small, resulting in the device being unable to start normally. Summary of the Invention

[0006] In view of the above situation, we propose a better solution, which not only limits the starting peak current of the AC power supply, but also reduces the power loss after the circuit works normally, and at the same time ensures that the power supply device can start normally under low-temperature conditions. The present invention discloses a rectifier bridge starting protection circuit. The protection circuit includes a rectifier bridge. The AC power supply charges the capacitor C0 through the power resistor R1 and the rectifier bridge. The energy storage capacitor C0, the power resistor R1, and the resistance value of the power resistor R1 is hardly affected by temperature. The power resistor R1 is connected in series on the loop between the AC power supply and the rectifier bridge. The energy storage capacitor C0 is connected across the rectifier bridge, and includes an IC control chip, an NMOS transistor N1, a NOMS transistor N2, a capacitor C1, a capacitor C2, an HB pin, an HO pin, and an HS pin.

[0007] As an improvement of the present invention, the gates of the NMOS transistor N1 and the NOMS transistor N2 are connected to both ends of the power resistor R1, and the sources and drains of the NMOS transistor N1 and the NOMS transistor N2 are connected respectively.

[0008] As an improvement of the present invention, the power supply pin VCC of the IC control chip is connected to the power supply generated after the internal circuit works normally. The HS pin is connected to the sources of the NMOS transistor N1 and the NOMS transistor N2. The HO pin is connected to the gates of the NMOS transistor N1 and the NOMS transistor N2. The HB pin is connected to the HS pin through the capacitor C1.

[0009] As an improvement of the present invention, the IC control chip includes an undervoltage detection module, a level shift module, a charge pump module, and a power drive module. The charge pump module is used to charge the capacitor C1. The level shift module is used to transfer the high-level signal output by the undervoltage detection module from the VCC voltage domain to the voltage domain between VHB and VHS. The undervoltage detection module is used to detect the voltage of VCC. The power drive module is used to enhance the current driving ability of the high-level signal in the voltage domain between VHB and VHS.

[0010] As an improvement of the present invention, the resistance value range of the power resistor R1 is 10Ω~10KΩ, and a suitable resistance value can be selected according to the requirement of the starting current size of the power supply device.

[0011] As an improvement of the present invention, the on-resistance value range of the NMOS transistor N1 and the NOMS transistor N2 is 5mΩ~10Ω, and a suitable on-resistance value can be selected according to the power size requirement when the device works normally.

[0012] As an improvement of the present invention, the capacitor C2 is connected between the VCC power supply pin and the GND pin, and the capacitor C2 is a filter capacitor for the power supply VCC.

[0013] The beneficial effects of the present invention are:

[0014] 1) Limit the starting peak current of the AC power supply to protect the safe operation of the rectifier bridge;

[0015] 2) The resistance value of the power resistor R1 remains basically unchanged under low-temperature conditions, ensuring that the device can start normally under low-temperature conditions;

[0016] 3) After the device operates normally, the current-limiting resistor is reduced to the on-resistance of two power NMOS transistors connected in series, greatly reducing the power consumption. Description of the Drawings

[0017] Figure 1 It is a schematic structural diagram of a rectifier bridge protection circuit in the prior art.

[0018] Figure 2 It is a schematic structural diagram of a rectifier bridge circuit with an added NTC resistor in the prior art.

[0019] Figure 3 It is a schematic structural diagram of a rectifier bridge starting protection circuit involved in the present invention. Detailed Embodiments

[0020] The following further clarifies the present invention in conjunction with the attached Figures 1 - 3 drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0021] Example: According to Figure 3As shown in the figure, a rectifier bridge startup protection circuit. The protection circuit includes a rectifier bridge. The AC power supply charges the capacitor C0 through the power resistor R1 and the rectifier bridge. There are an energy storage capacitor C0 and a power resistor R1. The resistance value range of the power resistor R1 is 10Ω~10KΩ, and a suitable resistance value can be selected according to the requirement of the startup current magnitude of the power supply device. The resistance value of the power resistor R1 is hardly affected by temperature. The power resistor R1 is connected in series on the loop between the AC power supply and the rectifier bridge. The energy storage capacitor C0 is connected across the rectifier bridge. It includes an IC control chip, an NMOS transistor N1, a NOMS transistor N2, a capacitor C1, a capacitor C2, an HB pin, an HO pin and an HS pin. The gates of the NMOS transistor N1 and the NOMS transistor N2 are connected to both ends of the power resistor R1. The sources and drains of the NMOS transistor N1 and the NOMS transistor N2 are connected respectively. The on-resistance value range of the NMOS transistor N1 and the NOMS transistor N2 is 5mΩ~10Ω, and a suitable on-resistance value can be selected according to the power magnitude requirement during normal operation of the device. The power supply pin VCC of the IC control chip is connected to the power supply generated after the internal circuit works normally. The HS pin is connected to the sources of the NMOS transistor N1 and the NOMS transistor N2. The HO pin is connected to the gates of the NMOS transistor N1 and the NOMS transistor N2. The HB pin is connected to the HS pin through the capacitor C1. The IC control chip includes an undervoltage detection (UV) module, a level shift (LS) module, a charge pump (CP) module, and a power driver (Drv) module. The charge pump module is used to charge the capacitor C1. The level shift module is used to transfer the high-level signal output by the undervoltage detection module from the VCC voltage domain to the voltage domain between VHB and VHS. The undervoltage detection module is used to detect the voltage of VCC. The power driver module is used to enhance the current driving ability of the high-level signal in the voltage domain between VHB and VHS. The capacitor C2 is connected between the VCC power supply pin and the GND pin. The capacitor C2 is a filter capacitor for the power supply VCC.

[0022] Working principle: Before the power supply device starts, the voltage across the energy storage capacitor C0 is 0V, and the power supply VCC generated by the power supply device is also 0V. The control circuit IC is not working, and the HO pin outputs a 0V level relative to the HS pin. The power MOS transistors N1 and N2 are turned off. At this time, the AC power supply will charge the capacitor C0 through the power resistor R1 and the rectifier bridge. The peak charging current is limited by the power resistor R1 to Vac*1.414 / R1, ensuring the safe operation of the rectifier bridge. The resistance value of the power resistor R1 is hardly affected by temperature, so the power supply device can start normally under low-temperature conditions. When the voltage across the energy storage capacitor C0 is charged to a high enough level, the power supply device starts to work and generates the power supply voltage VCC. The capacitor C2 is the filter capacitor for the power supply VCC; the charge pump CP starts to work and charges the capacitor C1, and the charging voltage is VHB - VHS, and the specific voltage value is determined according to the gate control voltages of the MOS transistors N1 and N2. The voltages of the HS pin and the HB pin fluctuate following the AC power supply voltage.

[0023] The undervoltage detection (UV) module detects the voltage of VCC. When the voltage of VCC is high enough, the undervoltage detection (UV) module outputs a high-level signal. The level shift (LS) module transfers this high-level signal from the VCC voltage domain to the voltage domain between VHB and VHS. After the high-level signal enhances the current driving ability through the power drive (Drv) module, it is output from the HO pin. The voltage difference between the HO pin and the HS pin is approximately equal to the voltage difference between the HB pin and the HS pin, that is, equal to the voltage difference generated by the charge pump. The voltage difference between the HO pin and the HS pin turns on the power MOS transistors N1 and N2.

[0024] After the MOS transistors N1 and N2 are turned on, the on-resistances of the MOS transistors N1 and N2 are in series and then in parallel with the power resistor R1. Since the series on-resistance value 2Rdson of the MOS transistors N1 and N2 is much smaller than the resistance value of the power resistor R1, the resistance value of the power resistor R1 can be ignored. The AC power supply will supply power to the device through the very small on-resistance 2Rdson, greatly reducing the power loss.

[0025] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, unless otherwise clearly specified and defined, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] Finally, it should be noted that the above-described embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features. These modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A rectifier bridge starting protection circuit, the protection circuit comprising a rectifier bridge, an energy storage capacitor C0 and a power resistor R1. The AC power supply charges the capacitor C0 through the power resistor R1 and the rectifier bridge. The power resistor R1 is connected in series in the loop between the AC power supply and the rectifier bridge, and the energy storage capacitor C0 is connected across the rectifier bridge. It is characterized in that, The protection circuit further includes an IC control chip, an NMOS transistor N1, an NOMS transistor N2, a capacitor C1, a capacitor C2, an HB pin, an HO pin, and an HS pin; The VCC power pin of the IC control chip is connected to the internal circuit, the HS pin is connected to the sources of the NMOS transistor N1 and the NOMS transistor N2, the HO pin is connected to the gates of the NMOS transistor N1 and the NOMS transistor N2, and the HB pin is connected to the HS pin through the capacitor C1; The capacitor C2 is connected between the VCC power pin and the GND pin, and the capacitor C2 is a filter capacitor for the power supply VCC; The gates of the NMOS transistor N1 and the NOMS transistor N2 are connected across the power resistor R1, and the sources and drains of the NMOS transistor N1 and the NOMS transistor N2 are connected respectively; The IC control chip includes an undervoltage detection module, a level shift module, a charge pump module, and a power drive module. The charge pump module is used to charge the capacitor C1, the level shift module is used to transfer the high-level signal output by the undervoltage detection module from the VCC voltage domain to the voltage domain between VHB and VHS, the undervoltage detection module is used to detect the voltage of VCC, and the power drive module is used to enhance the current driving ability of the high-level signal in the voltage domain between VHB and VHS; The high-level signal is output from the HO pin after the current driving ability is enhanced by the power drive module.

2. The rectifier bridge starting protection circuit according to claim 1, characterized in that, The resistance value range of the power resistor R1 is 10Ω to 10KΩ.

3. The rectifier bridge starting protection circuit according to claim 1, characterized in that, The on-resistance value range of the NMOS transistor N1 and the NOMS transistor N2 is 5mΩ to 10Ω.

4. The rectifier bridge starting protection circuit according to claim 3, characterized in that, The voltages of the HS pin and the HB pin fluctuate following the AC power supply voltage.

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