Circuit arrangement for a resonant converter and method of operating said converter

• US 20050226010A1
• Filed: 05/09/2003
• Published: 10/13/2005
• Est. Priority Date: 05/15/2002
• Status: Active Grant

• Current Assignee: TP Vision Holding BV (TPV Technology Co., Ltd. (f/k/a Nanjing Huadong Electronics Information & Technology))
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Sauerlander, Georg, Durbaum, Thomas
• Granted Patent: US 7,190,596 B2
• Time in Patent Office: Days
• US Class Current: 363/21.20
• CPC Class Codes: H02M 1/0058 by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826
• CPC Class Codes: H02M 1/083 for the ignition at the zero crossing of the voltage or the current
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• CPC Class Codes: H05B 41/2828 using control circuits for the switching elements H05B41/2827 takes precedence
• CPC Class Codes: H05B 41/2856 against internal abnormal circuit conditions
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

The invention relates to a circuit arrangement for a converter (1) with switches (S1, S2) for chopping a DC voltage U1 into a chopped DC voltage U3, comprising control means for controlling the switch-on times of the switches (S1, S2), in which switch-on times of the switches (S1, S2) alternate with each other and are separated from each other by dead-time phases Ttot, and circuit elements comprising a resonant circuit having at least one capacitor (Cr) and at least one coil (Lr) for convening the chopped DC voltage U3 into an output voltage U2. To ensure a reliable and interference-free ZVS operation of such a circuit, a circuit arrangement and a method of operating such a circuit arrangement are proposed in which a value for the energy/charge remaining in the resonant circuit for switching the switch in the inductive mode of operation is determined and compared with a threshold value by means of a comparator (24), and in which the switches (S1, S2) are controlled in dependence upon the comparison result.

Claims

1. A circuit arrangement for a converter (1) with switches (S1, S2) for chopping a DC voltage U1 into a chopped DC voltage U3, comprising control means for controlling the switch-on times of the switches (S1, S2), in which switch-on times of the switches (S1, S2) alternate with each other and are separated from each other by dead-time phases T_tot, and circuit elements comprising a resonant circuit having at least one capacitor (C_r) and at least one coil (L_r) for converting the chopped DC voltage U3 into an output voltage U2, characterized in that means for determining the current I flowing in the resonant circuit are provided, in that the control means comprise a comparator (24) which compares a value dependent on the current I flowing in the resonant circuit with a threshold value, and in that the circuit means control the switching of the switches (S1, S2) in dependence upon the comparison result.

2. A circuit arrangement as claimed in claim 1, characterized in that means for determining the current gradient dI/dt of the current I flowing in the resonant circuit are provided, in that the control means comprise a comparator (24) which compares a value dependent on the current gradient dI/dt with a threshold value, and the circuit means control the switching of the switches (S1, S2) in dependence upon the comparison result.

3. A circuit arrangement as claimed in claim 1, characterized in that the means for determining the current I and/or the current gradient dI/dt are provided in the resonant circuit.

4. A circuit arrangement as claimed in claim 1, characterized in that the means for determining the current I and/or the current gradient dI/dt are provided on each switch.

5. A circuit arrangement as claimed in claim 1, characterized in that the means for determining the current I and/or the current gradient dI/dt comprise at least a resistor (W1, W2).

6. A circuit arrangement as claimed in claim 1, characterized in that the means for determining the current I and/or the current gradient dI/dt comprise at least a current transformer.

7. A circuit arrangement as claimed in claim 1, characterized in that the means for determining the current I and/or the current gradient dI/dt comprise at least a current-sense FET.

8. A circuit arrangement as claimed in claim 1, characterized in that MOSFETs are used as switches (S1, S2), and the current and/or the current gradient dI/dt is determined via the drain-source voltage at the MOSFETs.

9. A method of switching the switches (S1, S2) in a circuit arrangement as claimed in claim 1, characterized in that:

a value dependent on the current I flowing in the resonant circuit is determined and compared with a threshold value during the switch-on phase of a switch (S1, S2); and

the switches (S1, S2) can be alternately switched off until the current I has reached the threshold value.

10. A method of switching the switches (S1, S2) of a circuit arrangement as claimed in claim 2, characterized in that:

a value dependent on the current gradient dI/dt of the current I flowing in the resonant circuit is determined and compared with a threshold value during the switch-on phase of a switch (S1, S2); and

the switches (S1, S2) can be alternately switched off until the current gradient dI/dt has reached the threshold value.

11. A method as claimed in claim 9, characterized in that a switch-off of the active switch (S1, S2) is triggered at the latest when the threshold value is reached.

12. A method as claimed in claim 9, characterized in that a switch-on of the subsequent switch (S1, S2) is prevented after exceeding or falling below the threshold value.

13. A method as claimed in claim 9, characterized in that the threshold value is adjusted in dependence upon the input voltage U1, and is raised with an increasing input voltage U1.