LED lighting power supply based on single-stage PFC controller UCC28810

The development of LED technology and its application has exceeded the industry's expectations a few years ago. Currently, LED has begun to enter the field of general lighting. In terms of LED public lighting in mainland China, the application of LED street lights and highway tunnel lights is at the forefront of the world. From a global perspective, LED general lighting drive circuits must be powered by industrial frequency mains power (i.e., offline drive circuits). In terms of its topology, it is mainly an isolated flyback converter switching power supply solution. For LED street lights above 200W, a dual inductor single capacitor (LLC) half-bridge resonant topology is selected. In LED lighting drive power supplies below 100W, a single-stage PFC flyback circuit topology is the best solution. The UCC28810 general lighting power supply controller launched by Texas Instruments (TI) not only supports single-stage PFC flyback converters and Triac dimming, but also supports two-stage PFC power supply topologies.

1 UCC28810 pin functions and features

1. 1 UCC28810 package and pin functions

UCC28810 adopts 8-pin SO IC package, and the pin arrangement is shown in Figure 1.

Figure 1 UCC28810 pinout

In order to correctly apply UCC28810, you must understand the function of each pin, see Table 1.

Table 1 UCC28810 pin functions

1.2 Main features of UCC28810

UCC28810 is a single-stage PFC offline LED lighting power supply controller that can control flyback, buck or boost converters operating in critical conduction mode (C rM) and can interface with traditional wall dimmers. UCC28810 contains a transconductance voltage amplifier for feedback error processing, a current reference generator for generating a current command proportional to the input voltage, a current sensing comparator, PWM logic and a driver for driving an external power MOSFET.

UCC28810 provides over-voltage protection (OVP), feedback open circuit protection and enable circuit.

The VDD turn-on threshold voltage of UCC28810 is 15.6 V, the undervoltage shutdown threshold level is 9.7 V, the clamping voltage is 19 V, and the static operating current is 4 mA.

UCC28810 is used to control LED general lighting driver power supply. Applications include industrial lighting, commercial lighting, residential lighting, as well as street, road, parking lot lighting and architectural and decorative lighting.

2 34W single-stage PFC flyback LED constant current driver based on UCC28810

The 34W single-stage PFC flyback LED constant current driver circuit based on UCC28810 is shown in Figure 2. The AC input voltage range of this isolated single-stage flyback offline LED driver circuit with PFC is 180~265V, the output DC voltage is 10~48V, the output constant current is 700mA, and it can drive 3~13 LEDs connected in series. The maximum output power is 34W, the efficiency is 90%, and the line power factor PF>0.9.

Figure 2 34W single-stage PFC flyback LED constant current driver based on UCC28810

In Figure 2, the input terminal F1 is a fuse, L1, L2 and C3, C1 are input EMI filters, D1 is a bridge rectifier, D2, D3, R9, R14, R19, C9 form an input voltage detection circuit, R1 and R4 are startup resistors on the U2 (UCC28810D) pin VDD, R8, D7, C7, D8, R7, Q1 and D6, C6 form the U2 (pin VDD) bias regulated power supply circuit, Q2 is the primary power switch, R2, R3, C2, D4 connected in parallel on the primary winding of the transformer (between pins ④ and ⑤ of T1) form an RCD type clamp circuit on the drain of Q2, R23 connected in series on the source of Q2 is a primary current sensing resistor, and the T1 bias winding (terminals ① and ②) also provides the transformer zero energy (TZE ) detection signal (transmitted to the TZE pin of U2 via R21, R20, and C12).

D5, C4 and C5 form the secondary rectifier filter circuit. R5 is the output current sensing resistor, and U1 (U1B + U1A) is used as a current sensing amplifier to perform output constant current regulation. U3 is a photocoupler that isolates the feedback from the secondary to the primary. The winding between the secondary pins ⑨ and ⑩ of T1 and D9, R18, D12, Q3 and C10 form the secondary bias regulator to provide bias for U1 and U3. D10 is used as an output open circuit clamp (51 V) protection.

U2 detects the AC input voltage through the pin V INS and can force the peak switch current to track the changes in the input voltage, thereby improving the system power factor.

3 240W LED street light driver using UCC28810

UCC28810 not only has the control function of single-stage PFC flyback converter, but also supports independent PFC boost converter architecture. Figure 3 shows a 240W LED street lamp driver power system using UCC28810. The system mainly has three stages: after the bridge rectifier is the PFC boost follower stage based on UCC28810; the second stage is the constant current buck (Buck) stage based on UCC28811, which works in critical conduction mode (C rM) like the PFC stage; the third stage is the isolation stage, which is a half-bridge resonant LLC converter, using TPS92020 as the driver IC.

Figure 3 240W LED street light driver power system using UCC28810

The technical specifications of the isolated offline LED driver shown in Figure 3 are shown in Table 2.

Table 2 Design technical indicators

The half-bridge resonant LLC converter can adopt a multi-transformer configuration, as shown in Figure 4. The series input multi-parallel LED driving scheme shown in the figure is conducive to heat dissipation management and does not require feedback, becoming an important driving scheme for LED lighting modules.

Figure 4 Multi-transformer configuration

4 Triac dimming LED lighting power supply using UCC28810

For general LED lighting, the traditional triac dimming method is generally favored because the Triac dimmer circuit is simple and low cost. When LED lamps are used to replace incandescent lamps, the Triac dimmer on the incandescent lamp wall can be used to dim the LED. Figure 5 is a block diagram of the Triac dimming LED lighting power supply system based on UCC28810.

Figure 5 Block diagram of Triac dimming LED lighting power supply system based on UCC28810

Incandescent lamp is a kind of resistive load, but the LED driving power supply is completely different from that of incandescent lamp. Therefore, when using traditional Triac phase-controlled dimmer to dim LED, a special circuit must be added to detect the Triac dimming state to ensure that the necessary holding current (IH) is provided to Triac within the Triac conduction angle of the AC line half cycle, and to ensure that Triac is turned off when the AC line voltage passes through zero.

Figure 6 shows the input EMI filter circuit of the Triac dimming 25W LED lighting power supply. The common-mode and differential-mode LC input EMI filters composed of L1, L2 and C1, C2 are set to meet the EMI specification requirements. When the Triac dimmer is used, a damping network composed of L3 and R5 in series is connected across the inductor L2 to prevent oscillation between the Triac and the LC filter.

Figure 6 Input EMI filter and damping network

Based on the actual 25W Triac dimming LED lighting power supply shown in Figure 5, the AC input voltage range is 85~305V, the line power factor is >0.9, the output DC voltage is about 36V, the output constant current is 700mA, and 10 Cree XLamp7090XRE white light LEDs can be connected in series, and the system efficiency is 89%.

5 Summary

UCC28810 LED general lighting power supply controller supports single-stage PFC flyback converter circuit topology and traditional Triac phase control dimmer dimming. There are many such ICs, such as TPS92210. LED dimming has many ways such as PWM dimming, analog voltage dimming and Triac. For LED general lighting applications, Triac dimming solution is generally favored by people.