SMPS Control IC

www.DataSheet4U.com TEA1530AT GreenChip™II SMPS control IC Rev. 01 — 18 May 2005 Objective data sheet 1. General description The GreenChip™II is the second generation of green Switched Mode Power Supply (SMPS) controller ICs. Its high level of integration allows the design of a cost effective power supply with a very low number of external components. The TEA1530AT can be used in Fixed Frequency converter designs for low voltage, high current applications. At low power (standby) levels, the system operates in cycle skipping mode which minimizes the switching losses during standby. The proprietary high voltage BCD800 process makes direct start-up possible from the rectified universal mains voltage in an effective and green way. A second low voltage BICMOS IC is used for accurate, high speed protection functions and control. The TEA1530AT enables highly efficient and reliable supplies to be designed easily. 2. Features 2.1 Distinctive features s Universal mains supply operation (70 V to 276 V AC) s High level of integration, resulting in a very low external component count s Fixed frequency operation 2.2 Green features s Cycle skipping mode at very low loads; input power < 300 mW at no-load operation for a typical adapter application s On-chip start-up current source. 2.3 Protection features s s s s s s s Safe restart mode for system fault conditions Undervoltage protection (foldback during overload) IC OverTemperature Protection (OTP) (latched) Low and adjustable OverCurrent Protection (OCP) trip level Soft (re)start Mains voltage-dependent operation-enabling level General purpose input for latched or safe restart protection and timing, e.g. to be used for overvoltage protection (OVP), output short-circuit protection or system OTP. www.DataSheet4U.com Philips Semiconductors TEA1530AT GreenChip™II SMPS control IC 3. Applications s Printer & LCD adapters / chargers / supplies. The device can however also be used in all applications that demand an efficient and cost-effective solution up to 65 W. 4. Ordering information Table 1: Ordering information Package Name TEA1530AT SO8 Description plastic small outline package; 8 leads; body width 3.9 mm Version SOT96-1 Type number 5. Block diagram Fig 1. Block diagram © Koninklijke Philips Electronics N.V. 2005. All rights reserved. Objective data sheet Rev. 01 — 18 May 2005 2 of 22 www.DataSheet4U.com Philips Semiconductors TEA1530AT GreenChip™II SMPS control IC 6. Pinning information 6.1 Pinning Fig 2. Pin configuration: TEA1530AT (SOT96-1) 6.2 Pin description Table 2: Symbol VCC GND PROTECT CTRL SENSE DRIVER HVS DRAIN Pin description Pin 1 2 3 4 5 6 7 8 Description supply voltage ground protection and timing input control input programmable current sense input MOSFET gate driver output High Voltage Spacer drain of the external MOS switch, input for start-up current 7. Functional description The TEA1530AT is the controller of a compact flyback converter, with the IC situated at the primary side. An auxiliary winding of the transformer powers the IC after start-up; see Figure 3. © Koninklijke Philips Electronics N.V. 2005. All rights reserved. Objective data sheet Rev. 01 — 18 May 2005 3 of 22 www.DataSheet4U.com Philips Semiconductors TEA1530AT GreenChip™II SMPS control IC Fig 3. Typical configuration The TEA1530AT operates in multi modes; see Figure 4. Fig 4. FF-CCM operation Because of the fixed frequency mode, the internal oscillator determines the start of the next converter stroke. A cycle skipping mode is activated at very low power (standby) levels. © Koninklijke Philips Electronics N.V. 2005. All rights reserved. Objective data sheet Rev. 01 — 18 May 2005 4 of 22 www.DataSheet4U.com Philips Semiconductors TEA1530AT GreenChip™II SMPS control IC 7.1 Start-up, mains enabling operation level and undervoltage lock out Refer to Figure 8 and Figure 9. Initially, the IC is self supplying from the rectified mains voltage via pin DRAIN. Supply capacitor CVCC (at pin 1) is charged by the internal start-up current source to a level of about 4 V or higher, depending on the drain voltage. Once the drain voltage exceeds the Vm (mains-dependent operation-enabling level), the start-up current source will continue charging capacitor CVCC (switch S1 will be opened); see Figure 1. The IC will activate the power converter as soon as the voltage on pin VCC passes the Vstart level. At this moment the IC supply from the high voltage pin is stopped (green function). The IC supply is taken over by the auxiliary winding of the flyback converter. The moment the voltage on pin VCC drops below VUVLO (undervoltage lock out), the IC stops switching and performs a safe restart from the rectified mains voltage. In the safe restart mode the driver output is disabled and pin VCC voltage is recharged via pin DRAIN. 7.2 Supply management All (internal) reference voltages are derived from a temperature compensated, on-chip band gap circuit. 7.3 Current control mode Current control mode is used for its good line regulation behavior. The primary current is sensed across an external resistor and compared with the internal control voltage. The driver output is latched in the logic, preventing multiple switch-on. The internal control voltage is inversely proportional to the external pin CTRL voltage, with an offset of 1.5 V. This means that a voltage range from 1 V to approximately 1.5 V on pin CTRL will result in an internal control voltage range from 0.5 V to 0 V (a high external control voltage results in a low duty cycle). Vsense(max) (V) coa016 0.52 V Cycle skip active 25 mV 1V (typ) 1.5 V (typ) VCTRL (V) Fig 5. The Vsense(max) voltage as a function of VCTRL 7.4 Oscillator The fixed frequency of the oscillator is set by an internal current source and capacitor. © Koninklijke Philips Electronics N.V. 2005. All rights reserved. Objective data sheet Rev. 01 — 18 May 2005 5 of 22 www.DataSheet4U.com Philips Semiconductors TEA1530AT GreenChip™II SMPS control IC 7.5 Cycle skipping At very low power levels, a cycle skipping mode activates. An internal control voltage (Vsense(max)) lower than 25 mV will inhibit switch-on of the external power MOSFET until this voltage increases to a higher value; see Figure 5. 7.6 Continuous Conduction Mode (CCM) The IC operates in the so-called Fixed Frequency Continuous Conduction Mode (FF CCM). Pin DRAIN should be connected to the rectified Vi voltage; see Figure 8. 7.7 OverCurrent Protection (OCP) The primary peak-current in the transformer is measured accurately cycle-by-cycle using the external sense resistor Rsense. The OCP circuit limits the voltage on pin “Sense” to an internal level equal to 1.5V - Vctrl (also see section 7.3). The OCP detection is suppressed during the leading edge blanking period tleb , to prevent false triggering caused by the switch-on spikes. 7.8 Control pin protection If pin CTRL becomes open-circuit or is disconnected, a fault condition is assumed and the converter will stop switching immediately. Operation recommences when the fault condition is removed. 7.9 Adjustable slope compensation A slope compensation function has been added at pin CTRL; see Figure 6. The slope compensation function prevents sub-harmonic oscillation in CCM at duty cycles over 50 %. The CTRL voltage is modulated by sourcing a (non-constant) current out of pin CTRL and by adding externally a series resistor Rslopecomp. This increases the CTRL voltage proportionally with the on-time, which therefore limits the OCP level. A longer on-time results in a higher CTRL voltage, this increase in CTRL voltage will decrease the on-time. Slope compensation can be adjusted by changing the value of Rslopecomp. Slope compensation prevents modulation of the on-time (duty cycle) while operating in FF CCM. A possible drawback of sub-harmonic oscillation can be output voltage ripple. © Koninklijke Philips Electronics N.V. 2005. All rights reserved. Objective data sheet Rev. 01 — 18 May 2005 6 of 22 www.DataSheet4U.com Philips Semiconductors TEA1530AT GreenChip™II SMPS control IC Slope compensation current Rslopecomp CTRL 4 −1 5.6 V RCTRL control detect 0.63 V 001aaa830 Fig 6. Slope compensation 7.10 Minimum and maximum on-time The minimum on-time of the SMPS is determined by the LEB time (typical 400 ns). The IC limits the on-time to a maximum time by limiting the driver duty cycle to 70 %. So the maximum on-time is correlated to the oscillator time which results in an accurate limit of the minimum input voltage of the flyback converter 7.11 PROTECT and timing input The PROTECT input (pin 3) is a multi-purpose (high-impedance) input, which can be used to switch off the IC and create a relatively long timing function. As soon as the voltage on this pin rises above 2.5 V, switching stops immediately. For the timing function, a current of typically 50 µA flows out of pin PROTECT and charges an external capacitor until the activation level of 2.5 V is reached. This current source is only activated when the converter is not in regulation, which is detected by the voltage on pin CTRL (VCTRL < 0.63 V). A (small) discharge current is also implemented to ensure that the capacitor is not charged, for example, by spikes. A MOSFET switch is added to discharge the external capacitor and ensure a defined start situation. The voltage on pin CTRL determines whether the IC enters latched protection mode, or safe restart protection mode: • When the voltage on pin CTRL is below 0.63 V, the IC is assumed to be out of regulation (e.g. the control loop is open). In this case activating pin PROTECT (VPROTECT > 2.5 V) will cause the converter to stop switching. Once VCC drops below VUVLO, capacitor CVCC will be recharged and the supply will restart. This cycle will be repeated until the fault condition is removed (safe restart mode). • When the voltage on pin CTRL is above