STARplug

www.DataSheet4U.com TEA1620P STARplugTM Rev. 01 — 17 March 2004 Product data sheet 1. General description The TEA1620P is a Switched Mode Power Supply (SMPS) controller IC that operates directly from the rectified universal mains. It is implemented in the high voltage EZ-HV™ SOI process, combined with a low voltage BICMOS process. The device includes a high voltage power switch and a circuit for start-up directly from the rectified mains voltage. A dedicated circuit for valley switching is built in, which makes a very efficient slim-line electronic power-plug concept possible. In its most basic version of application, the TEA1620P acts as a voltage source. Here, no additional secondary electronics are required. A combined voltage and current source can be realized with minimum costs for external components. Implementation of the TEA1620P renders an efficient and low cost power supply system. 2. Features s s s s s s s s s s s s s s Designed for general purpose supplies Integrated power switch: 48 Ω and 650 V Operates from universal AC mains supplies: 80 V to 276 V Adjustable frequency for flexible design RC oscillator for load insensitive regulation loop constant Valley switching for minimum switch-on loss Frequency reduction at low power output for low standby power: <100 mW Adjustable overcurrent protection Undervoltage protection Temperature protection Short winding protection Safe restart mode for system fault conditions Simple application with both primary and secondary (opto) feedback Available in 8-pin DIP package. 3. Applications s s s s Chargers Adapters TV and monitor standby supplies PC peripherals. www.DataSheet4U.com Philips Semiconductors TEA1620P STARplugTM 4. Quick reference data Table 1: Symbol VCC(max) VDRAIN(max) IDRAIN RDSon Quick reference data Parameter maximum supply voltage maximum voltage at pin DRAIN supply current drawn from pin DRAIN drain-source on-state resistance Tj > 0 °C no auxiliary supply ISOURCE = −0.06 A Tj = 25 °C Tj = 100 °C fosc Tamb oscillator frequency range ambient temperature 10 −20 48 68 55.2 78.2 200 +85 Ω Ω kHz °C Conditions Min Typ 0.5 Max 40 650 Unit V V mA 5. Ordering information Table 2: Ordering information Package Name TEA1620P DIP8 Description plastic dual in-line package; 8 leads (300 mil) Version SOT97-1 Type number 9397 750 12577 © Koninklijke Philips Electronics N.V. 2004. All rights reserved. Product data sheet Rev. 01 — 17 March 2004 2 of 16 www.DataSheet4U.com Philips Semiconductors TEA1620P STARplugTM 6. Block diagram VCC 1 SUPPLY 8 DRAIN VALLEY TEA1620P GND 2 LOGIC 100 mV 7 n.c. PWM stop RC 3 OSCILLATOR THERMAL SHUTDOWN PROTECTION LOGIC POWER-UP RESET 1.8 U 6 SOURCE low frequency f blank overcurrent REG 4 2.5 V 10x short winding 0.75 V 0.5 V 5 AUX col006 Fig 1. Block diagram. 7. Pinning information 7.1 Pinning VCC GND RC REG 1 2 3 4 001aaa308 8 DRAIN n.c. SOURCE AUX TEA1620P 7 6 5 Fig 2. Pin configuration. 9397 750 12577 © Koninklijke Philips Electronics N.V. 2004. All rights reserved. Product data sheet Rev. 01 — 17 March 2004 3 of 16 www.DataSheet4U.com Philips Semiconductors TEA1620P STARplugTM 7.2 Pin description Table 3: Symbol VCC GND RC REG AUX SOURCE n.c. DRAIN Pin description Pin 1 2 3 4 5 6 7 8 Description supply voltage ground frequency setting regulation input input for voltage from auxiliary winding for timing (demagnetization) source of internal MOS switch not connected drain of internal MOS switch; input for start-up current and valley sensing 8. Functional description The TEA1620P is the heart of a compact flyback converter, with the IC placed at the primary side. The auxiliary winding of the transformer can be used for indirect feedback to control the isolated output. This additional winding also powers the IC. A more accurate control of the output voltage and/or current can be implemented with an additional secondary sensing circuit and optocoupler feedback. The TEA1620P uses voltage mode control. The frequency is determined by the maximum transformer demagnetizing time and the time of the oscillator. In the first case, the converter operates in the Self Oscillating Power Supply (SOPS) mode. In the latter case, it operates at a constant frequency, which can be adjusted with external components RRC and CRC. This mode is called Pulse Width Modulation (PWM). Furthermore, a primary stroke is started only in a valley of the secondary ringing. This valley switching principle minimizes capacitive switch-on losses. 8.1 Start-up and undervoltage lock-out Initially, the IC is self supplying from the rectified mains voltage. The IC starts switching as soon as the voltage on pin VCC passes the VCC(start) level. The supply is taken over by the auxiliary winding of the transformer as soon as VCC is high enough and the supply from the line is stopped for high efficiency operation. As soon as the voltage on pin VCC drops below the VCC(stop) level, the IC stops switching and restarts from the rectified mains voltage. 8.2 Oscillator The frequency of the oscillator is set by the external resistor and capacitor on pin RC. The external capacitor is charged rapidly to the VRC(max) level and, starting from a new primary stroke, it discharges to the VRC(min) level. Because the discharge is exponential, the relative sensitivity of the duty factor to the regulation voltage at low duty factor is almost equal to the sensitivity at high duty factors. This results in a more constant gain over the duty factor range compared to PWM systems with a linear sawtooth oscillator. Stable operation at low duty factors is easily realized. For high efficiency, the frequency is reduced as soon as the duty factor drops below a certain value. This is accomplished by increasing the oscillator charge time. 9397 750 12577 © Koninklijke Philips Electronics N.V. 2004. All rights reserved. Product data sheet Rev. 01 — 17 March 2004 4 of 16 www.DataSheet4U.com Philips Semiconductors TEA1620P STARplugTM To ensure that the capacitor can be charged within the charge time, the value of the oscillator capacitor should be limited to approximately 1 nF. 8.3 Duty factor control The duty factor is controlled by the internal regulation voltage and the oscillator signal on pin RC. The internal regulation voltage is equal to the external regulation voltage (minus 2.5 V) multiplied by the gain of the error amplifier (typical 20 dB or 10 ×). The minimum duty factor of the switched mode power supply is 0 %. The maximum duty factor is set to 75 % (typical value at 100 kHz oscillation frequency). 8.4 Valley switching A new cycle is started at the primary stroke when the switch is switched on (see Figure 3). After a certain time (determined by the RC oscillator voltage and the internal regulation level), the switch is turned off and the secondary stroke starts. The internal regulation level is determined by the voltage on pin REG. After the secondary stroke, the drain 1 voltage shows an oscillation with a frequency of approximately ----------------------------2π × L p C p Where: Lp is the primary self inductance on the drain node Cp is the parasitic capacitance on the drain node. As soon as the oscillator voltage is high again and the secondary stroke has ended, the circuit waits for a low drain voltage before starting a new primary stroke. The primary stroke starts some time before the actual valley at low ringing frequencies, and some time after the actual valley at high ringing frequencies. Figure 4 shows a typical curve for a reflected voltage N × Vo of 80 V. This voltage is the output voltage Vo (see Figure 5) transferred to the primary side of the transformer with the factor N (determined by the turns ratio of the transformer). Figure 4 shows that the system switches exactly at minimum drain voltage for ringing frequencies of 480 kHz, thus reducing the switch-on losses to a minimum. At 200 kHz, the next primary stroke is started at 33° before the valley. The switch-on losses are still reduced significantly. 9397 750 12577 © Koninklijke Philips Electronics N.V. 2004. All rights reserved. Product data sheet Rev. 01 — 17 March 2004 5 of 16 www.DataSheet4U.com Philips Semiconductors TEA1620P STARplugTM primary stroke secondary stroke secondary ringing drain valley secondary stroke A RC oscillator regulation level B col007 A: Start of new cycle with valley switching. B: Start of new cycle in a classical PWM system. Fig 3. Signals for valley switching. 40 phase (°) 20 001aaa311 0 −20 −40 0 200 400 600 f (kHz) 800 Reflected voltage at N × Vo = 80 V. Fig 4. Typical phase of drain ringing at switch-on. 9397 750 12577 © Koninklijke Philips Electronics N.V. 2004. All rights reserved. Product data sheet Rev. 01 — 17 March 2004 6 of 16 www.DataSheet4U.com Philips Semiconductors TEA1620P STARplugTM 8.5 Demagnetization The system operates in discontinuous conduction mode all the time. As long as the secondary stroke has not ended, the oscillator will not start a new primary stroke. During the suppression time tsuppr, demagnetization recognition is suppressed. This suppression may be necessary in applications where the transformer has a large leakage inductance and at low output voltages. 8.6 Protections 8.6.1 Overcurrent protection The cycle-by-cycle peak drain current limit circuit uses the external source resistor RI (see Figure 5) to measure the current. The circuit is activated after the leading edge blanking time tleb. The protection circuit limits the source voltage to Vsource(max), and thus limits the primary peak current. 8.6.2 Short winding protection The short winding protection circuit is also activated after the leading edge blanking time. If the source voltage exceeds the short winding protection voltage Vswp, the TEA1620P stops switching. Only a power-on reset will restart normal operation. The short winding protection also protec